V THE ANTHOCEROTE^ 139 



closely to Anthoceros. A difference may be noted, however, in 

 some details. Thus the form of the apical cell is like that of 

 Pellia epipJiylla, where the inner segments extend the whole 

 depth of the thallus, and the division into dorsal and ventral 

 segments is secondary. The formation of the wings begins 

 near the apex and is the result of the growth of the marginal 

 cells, which project strongly and divide rapidly by vertical 

 walls only. The walls of the cells are thickened at the 

 angles, and the surface view is curiously like a cross-section of 

 the collenchyma of many vascular plants. As in Anthoceros 

 mucilage slits are formed, sometimes on both surfaces of the 

 thallus, and through these the plant is infected with Nostoc, as 

 in the other Anthoceroteae. In Dendroceros the Nostoc colonies 

 are very large and cause conspicuous swellings upon the thallus. 

 All the species of Dendroceros, according to Leitgeb, are 

 monoecious, and the development of the sexual organs appears 

 to be the same as in AntJioceros. The antheridia are very large 

 and borne singly in cavities whose upper wall projects above 

 the surface of the midrib. So far as is known the origin and 

 development correspond closely to those of Anthoceros, except 

 that the stalk is much longer and has- but two rows of cells, 

 which probably indicates that but one longitudinal wall is 

 formed in the antheridial cell before the transverse walls that 

 separate stalk and capsule. Gemmae occur in some species 

 {D. cichoraceus, D. Javanicus), and are roundish cell masses 

 developed from single cells of the lamina. So far as could be 

 determined from incomplete material, the conclusion was 

 reached by Leitgeb that Dendroceros approaches Anthoceros very 

 closely in the development of the sporogonium. The origin of 

 the columella, which usually in the later stages is composed of 

 more than sixteen rows of cells, and the differentiation of the 

 archesporium, seem to be exactly the same, and the further 

 development of the large bulb-like foot and the formation of 

 the spores and elaters arc the same. The spores are larger, and 

 the elaters (Fig. 74, B) provided with distinct spiral bands. In 

 none of the species examined by Leitgeb did he find any traces 

 of stomata upon the capsule, and concludes that they are 

 entirely wanting in this genus, which in this respect, as well as 

 in the character of the elaters, approaches closely one section 

 of the genus Anthoceros. The spores, as in Pellia and 

 ConocepJialus, germinate within the capsule, and at the time of 



