IV. 



THE ANTHOCEROTES 



151 



and are larger than in Anthoceros. As in that genus, they are 

 thrown off when the archegonium opens. 



Tlie youngest embryo found was composed of four cells, 

 and presented quite a different appearance from the corre- 

 sponding stage in Anthoceros. It is impossible from this stage 

 to tell whether the first wall in the embryo is vertical or trans- 

 verse. This embryo consisted of four nearly equal quadrants, 

 instead of having the two upper cells larger than the lower 

 ones. By comparison with the older stages there is little doubt 

 that here the first transverse wall separates the foot from the 

 capsule, as in Sphcerocarpus, and that the upper cell develops 

 directly into the capsule instead of the latter being determined 

 by the second transverse walls. In the next youngest stages 



Fig. 82. — Notothylas orbicularis. A, B, Horizontal sections of the growing point with 

 young archegonia; C, cross-section of the apex of an archegonium, showing the 

 arrangement of the cover cells; D, longitudinal section of a nearly ripe arche- 

 gonium, X400. 



found (Fig. 83, B) the archesporium was already differentiated. 

 A comparison of this with the corresponding stage of Antho- 

 ceros shows conclusively that the two are practically identical 

 in structure. The columella, evidently formed as in Antho- 

 ceros, and as there made up of four rows of cells, is surrounded 

 by the archesporium cut off from the peripheral cells. Leit- 

 geb's surmise that the columella is a secondary formation is, 

 therefore, for N. orbicularis at least, entirely erroneous, and it 

 is extremely likely that when normal specimens of the other 

 species are examined from microtome sections, in the young 



