Proventriculus

“ Protoloma: the anterior margin of primaries.
Protomesal: applied to certain areolets in Hymenoptera, situated between costal cells and apical margin.
Prototergite: the foremost dorsal segment of abdomen.
Preto-thorax: = prothorax: q.v.
Prototype: a primitive form to which later forms can be traced.
Protractor: that which extends or lengthens out: applied to muscles.
Protuberance: any elevation above the surface.
Protuberant: rising or produced above the surface or general level.
Proventriculus: the posterior portion of crop: the gizzard. ”

“ Course of the Food.—The food first enters the mouth, after being picked up by aid of the beak. From here it passes through the pharynx and first portion of the esophagus to the crop, without mastication, as the bird is not provided with teeth. The food is passed from the crop by aid of its muscular walls as needed; thence through the second portion of the esophagus to the proventriculus, an expansion in the digestive tube just before it terminates in the gizzard. ”

“ The glandules, which are cylindrical, the largest 3 twelfths of an inch long, 1/2 twelfth in diameter, form a complete elongated belt. The muscular coat is also very thick, its inner 99 layer composed of transverse, its outer of longitudinal fibres, and the greatest thickness of the walls of the proventriculus is about 4 1/2 twelfths of an inch. The stomach, e, properly so called, is extremely small, being of a roundish, compressed form, 1 1/4 inches in length, and of the same breadth ”

“ The first, which is found to be a female, has the mouth narrow, measuring only 7 twelfths across; the tongue very long and extremely slender, trigonal, pointed, extending to within half an inch of the tip of the lower mandible, being 3 7/12 inches in length. The œsophagus, a b c d, which is 12 inches long, is narrow in its whole length, its diameter at the upper part being 6 twelfths, below the middle of the neck 8 twelfths. The proventriculus, b c, is nearly 1 inch long, 9 twelfths in its greatest diameter, bulbiform ”

“ Proboscis, 446. 725Procephalic lobes, 544. Proctodæum, 537, 547, 569. Prodoxus, 606. Progoneate myriopods, 21. Pronotum, 87. Pronucleus, 526. Propodeum, 163. Propupa, 627. Prosopistoma, 467. Prostheca, 61. Prothorax, 86. Protocerebrum, 231, 232; its representative in annelids, 227. Proventricular valvule, 313. Proventriculus, 306; “beak” of, 312; formation of, in imago, 682; use of, 311, 324, 325. Prussic acid, 374. Psephenus, 462, 473. Pseudoglomeris, 598. Pseudonychium, 97. Pseudo-tracheæ, 446. Psocus, 616. Psychodes, 474. Psylla, 361, 518; glandular hairs of, 192; nymph of, 163. ”

“ He heard once more the trip of her voice warbling a Provençal song, while the great ruin of the Roman arène came once more to his vision, with its tufting shrubs and battered arches rising grim and gaunt into the soft Southern sky; the church-bells of the town poured their sweet jangle on his ear again, the murmur of distant voices came floating down the wind, and again the pretty Provençal song fluttered on the balmy air; the coquettish turban was in his eye, the plump, soft hand of the pretty Provençal girl in his grasp, and her glossy locks touched his burning cheek. ”

“ In the former the prothallus produces one or more fern-plants vegetatively, the projection which develops into the sporophyte in many cases occupying the position of an archegonium. In some apogamous Ferns sporangia may occur on the prothallus and the vegetative organs of the sporophyte may also occur singly. In apospory the converse phenomenon is seen, the gametophyte springing vegetatively from the sporangium, receptacle of the sorus, or leaf-margin of the fern-plant. In a number of cases, though not in all, apospory appears to be correlated with a failure of the sporangia to develop. ”

“ The first generation proceeds directly from the spore, and consists of a simple green expansion which is short-lived and very small, not usually exceeding half the size of a small finger-nail. This prothallus, as it is termed, has small, root-like hairs which fix it to the earth or elsewhere. The prothallia are to be seen in large numbers on the sides of flower-pots in neglected greenhouses. Each little green scale is a young fern-plant during its sexual generation. The male and female organs are much the same shape as those of mosses. ”

“ Head (Fig. 36) : as in description for genus above. Prothorax. Pronotum (Fig. 36) moderately broad, as wide as head across eyes (WH/WP, mean both sexes: 0.973) longer than head (LP/LH, mean both sexes: 1.349) , wider than long (W/L: mean both sexes: 1.824) ; markedly cordiform and explanate, lateral margin beaded with seta at anterior third; base markedly constricted and lobed; anterior angles moderately produced, hind angle markedly acutely produced and setose; median line moderately defined, basal and apical transverse impressions punctate, punctures infuscated; surface smooth throughout. ”

“ A spore, for instance, can never produce a fern as a seed will always produce a flowering plant. In this respect they are like many insects that always have two or sometimes three different stages in their life history. Only by the complicated method of first a spore then the prothallus, from which archegonia and antheridia are produced, followed by the free swimming male cells fertilizing the female, can a fern reproduce itself. ”

“ The sexual generation is represented by a small green prothallus which lives for a short period only and dies after nursing the fern-plant through its earliest stages.
(b) Hydropterideae. Heterosporous water-ferns differing considerably in habit from the true ferns. Each megasporangium contains a single megaspore and several microspores are produced in each microsporangium. The gametophyte is represented by tissue more or less enclosed in the spore. [Genera Salvinia, Azolla, Marsilia, Regnellidium, Pilularia. See Chapter XXVI.]
Eufilicineae. ”

“ After a time, however, the cells are produced transversely as well as longitudinally, resulting in the formation of a flattened leaf-like expansion (Fig. 125, d) , a cellular structure, the so-called Prothallus, which can scarcely be distinguished from a young Marchantia. In this Prothallus are developed Archegonia and Antheridia: the union of the embryo-cell of the Archegonia and the spiral filament of the Antheridia gives rise to the new Fern, which may be seen growing out of the Prothallus (Fig. 126) , which soon passes away. ”

“ The prothallus is exceedingly small, being little more than a group of cells forming an antheridium. Should there be sufficient moisture about, the spermatozoids which are produced by the antheridium swim towards the archegonia in any female prothallus which may be near. Fertilization then takes place, and the final outcome is the young plant. Now and again in certain species it is seen that the megaspores develop to such an extent within the sporangium that fertilization [21] takes place, and even an embryo or young plant may be formed. ”

“ In several species the stem stele is endarch. Our knowledge of the leaves is very meagre: in B. forensis they were repeatedly branched and apparently bore small fleshy pinnules; the sporangia, though differing from those of recent ferns, may be compared with the spore-capsules of Osmundaceae as regards the structure of the annulus. The abundance of hairs on the stems and leaves of some species, the tracheal sheath in the sporangium described by Oliver [1131] as Tracheotheca (= Botryopteris?) ”

“ The prothallus is thus the first stage in the reproduction of ferns, a very simple stage, with only the faintest indication that the thallus might be considered the vegetative and its rhizoids perhaps the rootlike counterparts of foliage and roots of mature ferns. As we shall see presently, even this differentiation has not the significance that such a structure in flowering plants would indicate. There is not, as yet, the faintest indication of sexes that need to mate in order to produce their young. ”

“ For a time the plant is nourished by the prothallium, but as soon as it is sufficiently developed and vigorous enough to shift for itself, the prothallium dies away, and the fern maintains an independent existence. Eventually it produces fronds which bear on their lower surfaces the sporangia containing the minute spores from which spring the prothallia. ”

“ From the new stand-point of evolution through natural selection the facts in Sprengel's work took on a most important significance. Darwin now reaffirmed the Sprengel theory so far as the necessity of the insect was concerned, but showed that all those perplexing floral conditions which had disproved Sprengel's assumption, instead of having for their object the conveying of pollen to the stigma of the same flower, implied its transfer to the stigma of another, cross-fertilization being the evident design, or evolved and perpetuated advantage. ”

“ Ferns usually produce their little green prothallia above ground, and the perfect plant generally has a creeping rhizome or underground stem. Some, however, have strong, erect, woody stems, such as we see in the tree ferns of tropical and sub-tropical countries. The horsetails and the club-mosses are also produced from prothallia that are formed above ground. The perfect plants of the former have branching underground stems which give off numerous roots, and send up annually green, jointed, aërial stems that bear whorls of fine leaves, each whorl forming a toothed, ring-like sheath. ”

“ The embryo which results from the union grows up (Fig. 147, B) into an ordinary fern plant, one being borne by each prothallus. In its young stages it is parasitic on the prothallus, i.e. it depends entirely upon the prothallus for its nutrition; but it soon develops a little leaf (b) and a root (w) , and henceforth feeds itself. When the young fern is well established in [Pg 189] independent life, the prothallus shrivels up and dies. The subsequently-formed roots of the fern are not branches of the primary root, but spring from the bases of the leaves. ”

“ The leaves in these species are unfolded from the sides—a totally distinct plan from that to be observed in all the Ferns which have been described, where the frond and its divisions are unrolled upwards. The prothallus is a small underground body destitute of chlorophyll. The fertile leaves are distinguished from the [12] barren ones by the production of a special branch which bears the fructification. The sporangia are large. ”

“ One group, the water ferns (Rhizocarpeæ) , produce two kinds of spores, large and small. The former produce male, the latter female prothallia. In both cases the prothallium is small, and often scarcely protrudes beyond the spore, and may be reduced to a single archegonium or antheridium (Fig. 71, B, C) with only one or two cells representing the vegetative cells of the prothallium (v) . The water ferns are all aquatic or semi-aquatic plants, few in number and scarce or local in their distribution. The commonest are those of the genus Marsilia (Fig. 71, A) , looking like a four-leaved clover. ”

“ Plants more or less fern-like consisting of a stem with a single leaf. In Ophioglóssum the leaf or sterile segment is entire, the veins reticulated and the sporangia in a simple spike. In Botrýchium the sterile segment is more or less incised, the veins free, and the sori in a panicle or compound or rarely simple spike. Sporangia naked, opening by a transverse slit. Spores copious, sulphur-yellow. ”

“ The spore produces the small green prothallium by cell-division in the usual way, and this completes the cycle of fern life.
The alternation of generations, which is perhaps most clear and typical in the case of the fern, becomes less distinctly marked in the plants of higher organization and type.
Thus in the Rhizocarpæ there are two kinds of spores, microspores and macrospores, producing prothallia which bear respectively antheridia and archegonia; in the Lycopodiaceæ, the two kinds of spores produce very rudimentary prothallia ”

“ The spores germinate on moistened ground. In a conservatory they may be found germinating on a damp wall or on the edges of a well-watered flower-pot. Instead of directly forming a fern-plantlet, the spore grows first into a body which [Pg 160] closely resembles a small Liverwort. This is named a Prothallus (Fig. 509) : from some point of this a bud appears to originate, which produces the first fern-leaf, soon followed by a second and third, and so the stem and leaves of the plant are set up. ”

“ The dehiscence of the sporangium is almost transverse, as in the Polypodiaceae, but the annulus is slightly oblique. The prothalli correspond to those of the next group.
Polypodiaceae.—This group, which contains the remaining ferns, includes a number of distinct lines of descent and will doubtless require subdivision as our knowledge of the morphology of the genera classed in it becomes extended. Space will not allow of an account of the progress already made in this direction. The stem in the more primitive forms has a tubular stele (solenostele) ”

“ Vernicle is 'a diminutive of Veronike (Veronica) , a copy in miniature of the picture of Christ, which is supposed to have been miraculously imprinted upon a handkerchief preserved in the church of St. Peter at Rome.... It was usual for persons returning from pilgrimages to bring with them certain tokens of the several places which they had visited; and therefore the Pardoner, who is just arrived from Rome, is represented with a vernicle sowed on his cappe.'—Tyrwhitt. See the description of a pilgrim in Piers Plowman, ed. ”

“ Spores developing into flat or irregular prothallia, which bear the reproductive organs (antheridia and archegonia) ; flowers and seeds none. 1. Spores produced in sporanges, which are borne on the back of a leaf, in spikes or panicles, or in special conceptacles. Order 1. Filicales. Spores all of one sort and size (isosporous families) . Vernation erect or inclined; sporanges in spikes, or panicles, opening by a transverse slit. Fam. 1. Ophioglossaceae. Vernation coiled; sporanges reticulated, usually provided with a ring (annulus) . ”