ii8 



MOSSES AND FERNS 



CHAP. 



am- 



which and the bud there is a space of some size. Later the 

 young branch grows more rapidly than the sheath and breaks 

 through it. 



The non-sexual reproduction of the acrogynous Hepaticae 

 may be brought about either by the separation of ordinary 

 branches through the dying away of the older parts of the 

 stem, or in a few cases observed (Schiffner (i), p. Gy) new 

 plants may arise directly from almost any point of a leaf or 



stem. Gemmae are known in a 

 large number of species. These 

 in most of the better known 

 cases are very simple unicellular 

 or biceilular buds arising often 

 in great numbers, especially 

 from the margins and apices of 

 leaves. Curious discoid multi- 

 cellular gemmae have been dis- 

 covered in a number of species, 

 especially in several tropical ones 

 investigated by Goebel (i6). 

 Gemmae upon the thallus of Le- 

 jeimia metizgeriopsis are of this 

 character, and similar ones are 

 found in Cololejeimia Goebelii. 

 In the latter (Fig. 60, B) the 

 gemma is a nearly circular cell 

 plate attached to the surface of 

 the leaf by a stalk composed of 

 (X about 40). B, a West Indian a siugle Cell. The first wall in 



Lejeunia, the lower leaf-lobes. X, ,, ,. . , . 



modified as water-sacs (X75). ^^^^ yOUUg gemma dlVldcS it 



into two nearly equal cells, in 

 each of which a two-sided apical cell is formed, so that like the 

 gemma of MarcJiantia there are two growing points. There 

 are usually four cells that differ from the others in their thicker 

 walls and projecting on either side of the gemma above the 

 level of the otlier cells. These serve as organs of attachment, 

 perhaps by the secretion of mucilage, and by them the young 

 plant adheres to the surface of the fern leaf upon which it 

 grows. The development of the gemmae, whether unicellular 

 or multicellular, resembles very closely that of the germinating 

 spores. 



Fig. 62. — A, Lejetmia sp., showing the 

 ventral leaves, or amphigastria, am 



