. The structure and development of mosses and ferns (Archegoniatae). were not more than 3 mm. in length. The exact originof the cell which the antheridia develops could not be madeout, as none of my sections showed the youngest (2) observations upon A. Icevis, however, and myown on A. Pearsoni and Notothylas valvata, as well as a studyof the older stages in A. fusiformis, leave no doubt that in thisspecies as in the others the antheridia are endogenous, and thewhole group of them can be traced back to a single cell. Theyarise close to the growing point, and the cell from which
. The structure and development of mosses and ferns (Archegoniatae). were not more than 3 mm. in length. The exact originof the cell which the antheridia develops could not be madeout, as none of my sections showed the youngest (2) observations upon A. Icevis, however, and myown on A. Pearsoni and Notothylas valvata, as well as a studyof the older stages in A. fusiformis, leave no doubt that in thisspecies as in the others the antheridia are endogenous, and thewhole group of them can be traced back to a single cell. Theyarise close to the growing point, and the cell from which they IV. THE ANTHOCEROTES i2g arise is the inner of two cells formed by a transverse wall in asurface cell. The outer cell (see Figure 67, 1>) divides almostimmediately by another wall parallel with the lirst, S(j that thegroup of antheridia is separated by two layers of cells fromthe surface of the thallus. The inner cell in A. Pcarsoni atonce develops into an antheridium; but in most species thecell divides first by a longitudinal wall into two, each of which. Fig. 67.—Anthoceros Pearsoni. Development of the antheridium: A, apex of thethallus, with very young antheridium, X about 500; B, a somewliat older stage;C, still older stage, somewhat less highly magnified; D, an older, but still im-mature antheridium, X about 200. generally divides again, so that there are four antheridiummother cells, all, how^ever, unmistakably the product of a singlecell, and if a comparison is to be made with the antheridium ofany other Liverwort, the antheridium in the latter is homol-ogous, not with the single one of Anthoceros, but with thewhole group, plus the two-layered upper wall of the cavity inwhich they lie. The first divisions in the antheridium are the same as thosein the original cell, , the young antheridium is divided longi-tudinally by two intersecting walls, and the separation of the9 I30 MOSSES AND FERNS CHAP. stalk from the upper part is secondary; indeed in the earhest
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