72 MOSSES AND FEIGNS chap. 



that, while still retaining the flattened thalloid character, yet 

 show the first formation of lateral appendages which represent 

 the leaves of the true foliose forms. In the latter the axis is 

 slender, and the leaves usually in three rows and relatively large. 



The archegonia correspond closely in their development to 

 those of the Marchantiaceae, and in the lower (anacrogynous) 

 forms arise in much the same way from surface cells of the 

 dorsal part of the younger segments, and the apical cell is not 

 directly concerned in their formation. The archegonia in 

 these thus come to stand singly or in groups upon the 

 dorsal surface of the thallus, whose growth is not interrupted 

 by their development. In the higher leafy forms (Junger- 

 manniaceai acrogynse) they occur in groups at the end of 

 special branches, whose apical cell finally itself becomes the 

 mother cell of an archegonium, and with this the growth in 

 length of the branch ceases. 



The antheridia differ essentially in their first divisions from 

 those of the Marchantiaceae. After the first division in the 

 mother cell, by which the stalk is cut off from the antheridium 

 itself, the first wall in the latter, in all forms investigated 

 except Sphcerocarpus and Riella, is vertical, instead of horizon- 

 tal, and the next formed walls are also nearly vertical. The 

 ripe antheridium is usually oval in outline and either nearly 

 sessile or provided with a long pedicel. The spermatozoids 

 are as a rule larger than in the Marchantiaceae, and show more 

 numerous coils, but like them are always biciliate. 



The embryo differs in its earliest divisions from that of the 

 Marchantiaceae. The first transverse wall divides the embryo 

 into an upper and lower cell, but of these the lower one, except 

 in Sph(zrocarpus and Riella, takes no further part in the 

 development of the sporogonium, but either remains undivided 

 or divides once or twice to form a small appendage to the base 

 of the sporogonium. In the upper cell the first wall may be 

 either vertical {i.e. Pellia and most anacrogynous forms), or it 

 may be transverse. From the upper of the two primary cells 

 not only the capsule but the stalk and foot as well are formed. 

 The development of these different parts varies in different 

 forms, and will be taken up when considering these. 



All of the Jungermanniaceae, except the Rielleae, possess 

 perfect elaters, but in the latter these are represented merely 

 by sterile cells that probably serve simply for nourishing the 



