The Anatomy of Isoetes

Abstract

There is no group of plants among pteridophytes whose anatomy has occasioned so much discussion as the genus Isoetes. The most recent writers, FARMER on I. iacustris, R. WILSON SMITH On I. echiinospora, and SCOTT and HILL on I. Hystrix, disagree in many points. In view of the lack of harmony, both of observation and interpretation, it has seemed advisable to make a comparative investigation of the anatomy of several American species. HistoricalThe literature on the anatomy of Isoetes began in i840 with a paper by VON MOHL (24).Although he recognized the lycopod affinities of Isoetes, he noted several important points of difference, in the arrangement and structure of the roots, and in the nature of the cambium products. Ever since that day the question of the nature of the cambium activity has afforded a fertile field for discussion, and it is with that subject that this pa-per is chiefly concerned. VON MOHL regarded the whole of the secondary growth as parenchymatous, and states that, as in other vascular cryptogams, there is no increase in thickness of the wood. The next significant work was that of HOFMEISTER (I6) in i857. In discussing the cambium products he says (p. 36i): "The effect of the yearly renovation of the cambial layer is not only to increase and renew the cortical tissue, but new spiral cells also become added, although only sparingly, to the wood of old vigorous plants. Individual cells of the cambium, separated by two or three cambium cells from the older principal mass of the wood, often exhibit thickenings of the walls, which by their delicacy and want of color betray their undoubted recent origin." In i873 appeared Russow's Vergleichende Untersuchungen der Leitbiindel-Kryptogamen (i8), with a discussion of the anatomy of I. lacustris, I. echinospora, and I. Hystrix. This paper has had great influence on subsequent work, and to Russow's work may be attributed the cur-II] [Botanical Gazette, vol. 47 This content downloaded from 044.224.250.rent conceptions of the nature of the cambium products, i. e., that the cambium produces cortex externally to itself, but internally it produces a tissue which he calls the "prismatic layer," and this he regards as being made up of phloem cells, tracheids, and parenchyma. HEGELMAIER (12), writing in i874, is inclined to question Russow's interpretation, but adds that no decisive grounds can be given against the interpretation of the Dauerzellen as soft bast. FARMER (9) published in i899 a very full discussion of I. lacustris. He seems reluctant to accept Russow's theory of the nature of the cambium products, but does not offer another. After quoting Russow he adds: "Quite apart from the fact that it is produced internally to the cambium and would, from the point of view of its position, be anomalous, its structure is remarkably complex and heterogeneous." In discussing the structure of the "prismatic layer" he says:The zone-like arrangement consists in alternations of tubular thin-walled cell-rows of varying thickness, whose cell contents are clear and water...

A Comparative Study of Stigmarian Appendages and Isoetes Roots

“…Comparison of stigmarian appendages and the roots of isoetes. -The roots of Isoetes, which have been described by Scott and Hill (1900), Stokey (1909) and many other authors, are much smaller than the appendages of Stigmaria. They both have dichotomous branching (fig.…”

MORPHOLOGY OF THE MEGAGAMETOPHYTE AND THE EMBRYO SPOROPHYTE OF ISOETES LITHOPHILA

“…The change from the apical to the basal type of tissue is often quite abrupt in this species, but there is no evidence at any stage of a diaphragm separating the two portions of the gametophyte (text figs. 2,16).…”

“…Later morphological studies on Isoetes have been made by Bruchrnann (4), Belajeff (2), Kienitz-Gerloff (II), Farmer (8), Campbell (5), Arnoldi (I), Goebel (9), Scott and Hill (14), Smith (IS), Stokey (16), West and Takeda (17), and, in a limited way, by others. But accounts of detailed studies of the female gametophyte and the embryo sporophyte are pretty well limited to the work of Hofmeister (10), Kienitz-Gerloff (II), Farmer (8), Campbell (5), and Arnoldi (I).…”

Stipe anatomical studies on selected pteridophytes of South India

“…Stipe characters have proved to be of great value on the identity of a taxon (Lucansky and White 1974, Srivastava 2008a, b, Wagner 1997, Walker 1957, 1960. Other important works on the anatomy of pteridophytes are Bir (1977), Bir and Devi (1971), Paulillo (1963), and Stokey (1909). However, the characteristics of the stipe still remain to be studied in the case of a number of fern species.…”