Marshall Avery Howe

Name: The Genus Riella, with Descriptions of New Species from North America and the Canary Islands
Author: Marshall Avery Howe

The Genus Riella, with Descriptions of New Species from North America and the Canary Islands (1903)

Summary

“The Genus Riella, with Descriptions of New Species from North America and the Canary Islands”, published in 1903, is a work by Marshall Avery Howe. It explores elements such as Riella, cell and spores.

Quotes from The Genus Riella, with Descriptions of New Species from North America and the Canary Islands (Marshall Avery Howe)

Marshall Avery Howe, The Genus Riella, with Descriptions of New Species from North America and the Canary Islands (1903)

“ In describing Riella Paulsenii, the first species of the genus known to occur outside of the Mediterranean region, Porsild expresses the surmise that the distribution of the genus may prove to be still more widely extended, which is well verified by the known existence at the present time of three specimens of Riella collected within the boundaries of the United States. ”

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Source: Wikisource

Marshall Avery Howe, The Genus Riella, with Descriptions of New Species from North America and the Canary Islands (1903)

“ The species of Riella are all aquatic, commonly growing entirely submerged, and it is doubtless this condition of growth which makes possible the leading peculiarity in form.
The growing point of a young plant or of a young branch of Riella is not apical in the ordinary sense of the word, but intercalary. The whole tissue of the young shoot appears to be meristematic at first and of one layer of cells. Later, the growth activities are concentrated at either one or two points on the margin of the shoot intermediate between its distal and proximal extremities. ”

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Source: Wikisource

Marshall Avery Howe, The Genus Riella, with Descriptions of New Species from North America and the Canary Islands (1903)

“ Our experiments in germinating the spores of Riella affinis have been more successful than those with the spores of Riella Americana, though they were not begun until December, 1902, five and a half years from the date of collection of the specimens. More than half of the spores experimented with germinated in a few days by being placed on a piece of wet filter-paper in a glass dish kept in a moist chamber at ordinary living-room temperatures. The germ-tube in practically all cases emerges, as in R. Americana, from the outer or more spiny face of the spore, usually near its middle. ”

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Source: Wikisource

Marshall Avery Howe, The Genus Riella, with Descriptions of New Species from North America and the Canary Islands (1903)

“ The genus Riella occupies a unique position among the Hepaticae. The striking peculiarities of its gametophytic phase have attracted the attention of such morphologists as Hofmeister, Leitgeb, and Goebel, in addition to the interest excited among those who have devoted themselves more exclusively to a study of the systematic relations of the Hepaticae. Riella helicophylla, an Algerian species, is alluded to in some of the standard botanical text-books as being peculiar among the liverworts in having a leaf-like lamina or wing disposed spirally in relation to the axis or stem. ”

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Source: Wikisource

Marshall Avery Howe, The Genus Riella, with Descriptions of New Species from North America and the Canary Islands (1903)

“ The new cells formed on the upper or distal side of the growing point now contribute to the growth of the unistratose wing, which is dorsal in position. The new cells formed on the lower or proximal side of the growing point go to constitute the multistratose stem, which is ventral in position. ”

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Source: Wikisource

Marshall Avery Howe, The Genus Riella, with Descriptions of New Species from North America and the Canary Islands (1903)

“ If two growing points on opposite margins of a young shoot persist, a double or twin plant is formed, the two branches of the axis bearing a single continuous dorsal wing. If, however, only one growing point persists, the plant or branch is apparently one-sided, with stem on one side and wing on the other, though in reality the wing is dorsal and the stem ventral.
On account of the absence of elaters, Riella was at first placed with the Ricciaceae, together with Sphaerocarpus, in which, likewise, elaters are not developed. ”

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Source: Wikisource

Marshall Avery Howe, The Genus Riella, with Descriptions of New Species from North America and the Canary Islands (1903)

“ The larger-celled part, derived from the apex or distal end of the initial trichome, becomes at about this time more than one cell thick in its middle and terminal regions and shows papilliform outgrowths, the beginnings of the root-hairs. The smaller-celled portion derived from the base or proximal end of the initial trichome remains only one cell thick except in the isthmus of constriction where it finally, in part at least, becomes two or more cells thick. F. 16 shows a well-developed gemma inverted as regards its original relations to the axis of the gametophyte. ”

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Source: Wikisource

Marshall Avery Howe, The Genus Riella, with Descriptions of New Species from North America and the Canary Islands (1903)

“ The basal cells afterward grow out and divide in such a way as to give the body a free margin throughout its periphery, though it remains attached to the axis for a considerable time by a single cell on its proximal surface. ”

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Source: Wikisource

Marshall Avery Howe, The Genus Riella, with Descriptions of New Species from North America and the Canary Islands (1903)

“ Our specimens of R. affinis are prostrate and more or less entangled with mud and are so delicate and fragile that it is quite possible that the measurements in the above description may fail to do full justice to the height of the plant. It may be remarked that in occasional capsules the spores though showing a well-developed brown coloration have short spines or papillae much like those of R. Cossoniana; such spores are always smaller than is normal for the species and are probably immature or else have ripened under abnormal conditions. ”

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Source: Wikisource

Marshall Avery Howe, The Genus Riella, with Descriptions of New Species from North America and the Canary Islands (1903)

“ The forms assumed by the young gametophytes are extremely varied and are doubtless determined to a considerable extent by the conditions of illumination, though no exact investigations were undertaken to demonstrate the influence of light in this matter. ”

Marshall Avery Howe

Summary

Quotes from The Genus Riella, with Descriptions of New Species from North America and the Canary Islands (Marshall Avery Howe)

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