. The structure and development of mosses and ferns (Archegoniatae). which time they showed no diminution of form ordinary adventitious shoots, but there are alsospecial gemmae developed in many of them, often in great num-bers. In an undetermined species of Hymenophyllum col-lected In the Hawaiian Islands (Fig. 216) these gemmae oc-curred very abundantly upon prothallia that had ceased to formsexual organs. A marginal cell grows out and curves upward, THE HOMOSPOROUS LEPTOSPORANGIAT^ 375 and the tip is cut off by a transverse wall from the basal the terminal cell are next
. The structure and development of mosses and ferns (Archegoniatae). which time they showed no diminution of form ordinary adventitious shoots, but there are alsospecial gemmae developed in many of them, often in great num-bers. In an undetermined species of Hymenophyllum col-lected In the Hawaiian Islands (Fig. 216) these gemmae oc-curred very abundantly upon prothallia that had ceased to formsexual organs. A marginal cell grows out and curves upward, THE HOMOSPOROUS LEPTOSPORANGIAT^ 375 and the tip is cut off by a transverse wall from the basal the terminal cell are next formed a series of vertical walls,which transforms it into a row of cells extended at right anglesto the axis of the pedicel. One of the central cells now bulgesout laterally, and this papilla is cut off by an oblique wall andforms the beginning of a short lateral branch, so that the fully-developed bud has somewhat the form of a three-rayed star,and in this condition becomes detached and growls into a newprothallium. The prothallia formed in this way often do not. Fig, 2i6.—Hymenophyllum (sp). Margin of a prothallium with numerous gemmae k;X8s; B, a young gemma, X260; st, its stalk. develop a flat thallus, but may remain filamentous, and eachray may produce antheridia either terminally or laterally (, C). In case a flat thallus is formed, only one or some-times two of the rays grow out in this form, the other havingonly a limited growth, and terminating in a short rhizoid. Inshort, the process is very similar to that in the germinatingspores. 376 MOSSES AND FERNS CHAP. The Sexual Organs Bower (8) has investigated the structure of the anther-idium in Trichomanes, and Goebel (lo) in both Trichomanesand Hymenophyllum. My own study of their developmenthas been confined to an undetermined species of Hymenophyl-lum from the Hawaiian Islands, but the results of my observa-tions agree entirely with those of other observers. The anther-idia arise mainly upon the margin of the
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