Petiole

“ At the tips these leaflets droop slightly, but at that end where they spring out of the midrib, they are stiff and rigid. The petiole, or leafstalk itself, is long, straight, and thick; and where it clasps the stem or trunk, is swollen out to a foot in width, hollowed, or concave on the upper side. A full-grown leaf, with its petiole, is a wonderful object to look upon. The stalk is a solid beam full twelve feet in length, and the leaf has a diameter of nearly as much. Leaf and stalk together make a load, just as much as one man can carry upon his shoulders! ”

“ If they catch nothing, the whole petiole ultimately grows straight. Both the medial and lateral petioles are sensitive; and the three branches, into which the basi-lateral petioles are generally subdivided, likewise are sensitive. The basal portion of the main petiole between the stem and the first pair of leaflets is less sensitive than the remainder, but it will clasp a stick when in contact. On the other hand, the
A young leaf of Clematis viticella. ”

“ Abdomen: the petiole and the following segment red, the base of the third also slightly red; the three apical segments obscurely blue, with a thin glittering pile.
The male differs in having the legs black, their articulations only being ferruginous; the head entirely black with the face densely covered with silvery-white pile. The thorax is sculptured as in the other sex; the petiole more elongate and slender, the basal joint black, the second and the first segment ferruginous beneath; the rest of the abdomen blue. ”

“ It is also supposed that the vessels of the petiole gradually become woody, and incapable of freely transmitting the sap; it therefore stagnates, the vessels become overloaded, and the parts which connect the stem and the leaf crack at the insertion of the petiole. ”

“ When the plant is not in its most lively state, the under surface of the intumescence of the subleaflet (b, Fig. 2,) and the upper surface of the intumescence of the petiole (a, Fig. 6,) may be pricked with a needle, without producing action. But if the opposite surfaces, those namely, which change colour and are shortened when the petiole is depressed and the subleaflets folded, are touched with the point of the needle these actions are instantaneously produced. ”

“ However, not to be a water-lily is not so bad if one may be classed with the fringed and closed gentians which are to bloom later on the landward edges of the bog. As the little blossom fades at nightfall, its short stalk curls back beneath the water to ripen the seeds there, hung just beneath the leaf from a peculiar bulb-like nodule just an inch or so down on the petiole. ”

“ A full-grown leaf of this tree is quite a load for one man to carry. The petiole, or leaf-stock, is a solid beam ten or twelve feet long, while the leaf or fan itself measures nine or ten across. The fruit, in bunches of three hundred and upward, perfectly resembles the cones of the white pine. ”

“ The several terminal branches of the petiole bearing the much reduced leaflets (a, b, c, d) are highly sensitive, for a loop of thread weighing only the one-sixteenth of a grain (4.05 mg.) caused them to become greatly curved in under 4 hrs. When the loop was removed, the petioles straightened themselves in about the same time. The petiole (e) was rather less sensitive; and in another specimen, in which the corresponding petiole bore rather larger leaflets, a loop of thread weighing one-eighth of a grain did not cause curvature until 18 hrs. ”

“ As the pulvinus is so indistinct at first, the movement probably does not then depend on the expansion of its cells, but on periodically unequal growth in the petiole. By the comparison of seedlings of different known ages, it was evident that the chief seat of growth of the petiole was in the upper part between the pulvinus and the blade; and this agrees with the fact (shown in the measurements above given) that the cells grow to a greater length in the upper than in the lower part. ”

“ Both serrations and glands are best studied in the middle of the sides of leaves, those at the base or apex often being crowded or wanting.
Petioles differ in length, thickness, rigidity, pubescence and color, so that this organ is often a substantial help in identifying varieties. Some say the color of the petiole is correlated with that of the fruit, as it certainly is in such extreme sorts as Snowball and Indian Cling, but it is doubtful whether this correlation goes further than groups and even here does not always hold. Stipules offer no distinguishing marks of importance. ”

“ The base of the petiole is hollow and in falling off exposes the winter bud. The multiple FRUIT forms a ball about 1 inch in diameter, which hangs on its flexible peduncle—3 to 5 inches long. During early spring the fruit ball breaks up, and the small nutlets are scattered widely by the wind.
The WOOD is hard and moderately strong, but decays rapidly in the ground. ”

“ Owing to this rising of the petioles, and the vertical sinking of the large leaflets, the leaves become crowded together at night, and the whole plant then exposes a much smaller surface to radiation than during the day.
Oxalis Plumierii.—In this species the three leaflets do not surround the summit of the petiole, but the terminal leaflet projects in the line of the petiole, with a lateral leaflet on each side. They all sleep by bending vertically downwards, but do not become at all folded. ”

“ Leaves scattered, four to six inches long, linear-cuneate, coriaceous, rigid, often truncated at the extremity, the margins coarsely dentato-serrated, almost spinulose, the base attenuated into a very slender, pale yellow-green petiole: the upper side is glabrous, dark green, and glossy, very obscurely veiny, below paler, the vein and veinlets glabrous, the areolæ or lacunes filled with white down. Flowers of an uniform, rather pale, and dull yellow, densely collected into a broadly-oblong, terminal head. Scales very hairy, deep orange. ”

“ An interesting feature is the absence of projecting teeth in the leaf-trace, a character in marked contrast to the ω form assumed by the petioles of Botryopteris forensis (fig. 319, G) and B. hirsuta. This leads Kidston to suggest that the vascular strand of the petiole tends “to become more simple ... as traced back in geological time.” The greater similarity in this species between the stele 443of the stem and that of the petiole is probably another mark of a more primitive type.
Fig. 307. Botryopteris antiqua: Petiolar vascular strand. (After Kidston: × 65.) ”

“ Stems short, tufted, slender. Leaves persistent, of leathery texture, the blade spathulate, channelled at the base, keeled behind, tapering down into the petiole, which is invested by whitish brown membranaceous sheathing bracts. Scape issuing from the bract, investing the leaf base, radical, about a foot high, stiff, pale green, thickly striate-blotched with purple, with one or two distant sheathing bracts, and surmounted by the curved six-ribbed ovary, which is dotted with purple. ”

“ Tropæolum pentaphyllum.—The plant observed by me had not the power of spirally twining, which seemed due, not to the want of flexibility in the stem, but rather to continual interference from the clasping petioles. An upper internode made three revolutions, following the sun, at an average rate of 1 h. 46 m. The main purpose of the revolving movement in all the species is manifestly to bring the petioles into contact with some supporting object. The petiole of a young leaf, after a slight rub, became curved in 6 m. ”

“ The petiole is stout, 1 to 2 inches long, grooved, and enlarged at the base.
The FLOWERS, which appear in March or April are of two kinds, usually borne on separate trees, the male flowers in dense round clusters, and the female flowers solitary.
The FRUIT, ripening in early fall, is a dark purple drupe, oblong or obovate in shape, about 1 inch long, with a thick, tough skin enclosing a flattened stone, and borne on a slender peduncle 3 to 4 inches long.
The WOOD is light, soft, and not strong. ”

“ Petiole 11⁄2-3in.; stipules with dense stellate canescene, pubescent towards the apex, varies greatly in regard to the pubescence of young shoots, leaves and inflorescence. Racemes 3-5-flowered. Flowers 3in. diam; Calyx-tube obconic, hairy, subspheroidal, mouth contracted, unenlarged lobes deltoid-ovate. Petals pinkish white. Nut pubescent.
Habitat. — Eastern Bengal and Eastern Peninsula, from Chittagong and Pegu to Singapur; not in Ceylon, nor in the Konkan.
Use: — The oleo-resin is applied externally to ulcers, ringworm, and other cutaneous affections (Watt.) ”

“ The effect of the unusual structure of the petiole is that the leaf, instead of being horizontal as in the P. alba and most trees, hangs vertically, and this again explains the similarity of the two surfaces, because the result is that both surfaces are placed under nearly similar conditions as regards light and air. Again, it will be observed that, if we attempt to arrange the leaves of the black poplar on one plane, they generally overlap one another; the extent is larger than can be displayed without their interfering with one another. ”

“ A petal often consists of two portions—the lower narrow, resembling the petiole of a leaf, and called the unguis or claw; the upper broader, like the blade of a leaf, and called the lamina or limb. These parts are seen in the petals of the wallflower (fig. 54) . The claw is often wanting, as in the crowfoot (fig. 55) and the poppy, and the petals are then sessile. According to the development of veins and the growth of cellular tissue, petals present varieties similar to those of leaves. Thus the margin is either entire or divided into lobes or teeth. ”

“ I have in my possession a leaf of Antirrhinum majus, and also a specimen of Pelargonium, wherein the blade of the leaf is funnel-like, and the petiole is cylindrical, not compressed, and grooved on the upper surface, as is usually the case. A comparison of the leaves of Pelargonium peltatum with those of P. cucullatum ('Cav. [Pg 23] Diss.,' tab., 106) will show how easy the passage is from a peltate to a tubular leaf. In these cases the tubular form may rather be due to dilatation than to cohesion. ”

“ The experiments already mentioned appear to explain the mode in which the elevation and depression of the petiole, and the divergence and approximation of the subpetioles are produced. It is probable that the contrivance for folding and expanding the subleaflets is of a similar nature. Mr. Burnett and myself conjectured that each subleaflet is raised by the under part of the intumescence that exists at its base, and [p081] depressed by some action of the upper portion of the same intumescence. ”

“ A petiole excited by an extremely slight weight sometimes bends a little, and then becomes habituated to the stimulus, and either bends no more or becomes straight again, the weight still remaining suspended. Petioles which have elapsed any object for some little time cannot recover their original position. ”

“ Moreover the whole end of the petiole or tendril, if it seizes nothing, bends after a time abruptly downwards and inwards, showing that its outer surface has gone on growing after the inner surface has ceased to grow. ”

“ Leaves all on long petioles, mostly once or twice or even three times divided into spreading lobes, long and narrow when few, shorter when more divided, obtuse or with short points, the whole leaf including the petiole from a few in. to above 1 ft. long, the lowest leaves as in the allied species usually entire. Flowering stems long and leafless, usually branched, the flowers small and distant. Perianth more incurved than in other species, not exceeding 2 lines, Stigma anteriorly produced on each side into a broad semicircular auricle or short broad lobe. ”

“ The young leaves change their position in a rather odd manner: when first developed the petioles are upturned, parallel to the stem; they then slowly bend downwards, remaining for a short time at right angles to the stem, and then become so much arched downwards that the blade of the leaf points to the ground with its tip curled inwards, so that the whole petiole and leaf together form a hook. If they come into contact with no object, they retain this position for a considerable time, and then bending upwards they reassume their original upturned position, which is retained ever afterwards. ”

“ Petioles of the Cottonwood.—The leaves of the Cottonwood as well as some other species of Populus have an interesting light relation. If one looks at a vigorous shoot, the leaves are seen to be arranged in the profile position around the stem. This is accomplished by means of a very simple device. The petiole is much flattened next to the blade and is quite flexible. The flattening is transverse to the plane of the blade and on this account the leaf will assume the vertical position, no difference in what way it is attached or twisted. ”

“ In these exotic orders I frequently find the genera so at loose ends that I cannot make the plants of our collection lie comfortably till I have given the genera a good shaking up. I should be tempted to do much more of this if I could work at Hooker’s, or in Paris. It is quite as well not, as it would cost no end of time....
I have found some Fouquiera seedlings up in the Garden. I am right about it; not Torrey. The leaf is not axillary and its petiole inclosed in the spine; but the spine is a hardened inferior portion of the petiole that persists, and from which the rest falls away clean.... ”