522 MOSSES AND FERNS chap. 



with the plant until the embryo has produced the cotyledons 

 and root." (/. c, p. 183). 



In S. apus, the strobili are shed in the early autumn, whether 

 fertilisation has occurred or not. 5". rupestris retains the stro- 

 bili through the winter, and fertilisation is effected in the spring. 



From some partial observations made by the writer upon 

 spores of a species (probably L. Bigelovii) from the dry 

 region of southern California, it looks very much as if, in this 

 species, the spores became completely dried up after the embryo 

 had already attained some size, and that the spores remained 

 in this condition through the dry season, the embryo resuming 

 its growth again in the autumn. 



The Adult Sporophyte 



The genus Selaginella is a very large one, but there is some 

 difference of opinion as to the number of species. Hierony- 

 mus (i) enumerates 559 species, while Underwood (4) says 

 the genus contains "about 335" species. The genus is usually 

 divided into two subgenera, Euselaginella (Homceophyllum 

 of Hieronymus) and Stachygynandrum (Heterophyllum, 

 Hieronymus). In the first are included those species in which 

 the leaves are all alike and arranged radially about the shoot, 

 which is generally more or less completely upright. 5". rupes- 

 tris, S. selaginoides and S. Bigelovii are examples. In Stachy- 

 gynandrum, which comprises the majority of the species, the 

 shoot is dorsiventral, and often prostrate. The leaves are 

 four-ranked, those of the two dorsal rows being much smaller 

 than the others (Fig. 302). The first type suggests the species 

 of Lycopodium of the type of L. annotinum, the second that of 

 L. complanatum or L. volubile. In many species there is a 

 creeping stem from which upright branches grow, much as in 

 many species of Lycopodium, but in others there is no clear dis- 

 tinction between these parts. TEe roots may arise directly 

 from the ordinary branches, but in many species, e. g., S. 

 Kraussiana, they are borne at the end of peculiar leafless 

 branches or rhizophores (Fig. 305, A). These, like the stem, 

 show an apparently regular dichotomous branching, which, 

 however, is really monopodial. The leaves, like those of Lyco- 

 podium, are small, more or less lanceolate in outline, and with a 

 single median vein. In the homophyllous forms the sporo- 



