TJic Genus Riccardia in Chile. 171 



stolons is perhaps associated with the fact that the plants are not 

 closely adherent to the suhstratum. The comparison of cross 

 sections brings out certain differences in histological structure. It 

 will at once be seen that the contrast in size between the superfi- 

 cial and interior cells is more marked in R. diversiflora than in 

 R. aittoica, owing mainly to the fact that its interior cells are con- 

 siderably wider. In R. autoica, moreover, the wings of the thallus, 

 especially on the ultimate branches, attain a greater width and are 

 often distinctly crenulate, while in R. diversiflora the wings are 

 less distinctive and usually entire or nearly so. It is in the sexual 

 branches, however, that still more important differences can be 

 made out, even if the bisexual branches of R. diversiflora are left 

 out of consideration. In R. autoica, as seen by comparing Figs. 

 7, H, and 9, E, the smaller cells of the male inflorescence give the 

 whole structure a more compact appearance. The suberect or con- 

 nivent wings and the more complicated partitions between the 

 chambers are likewise very distinctive. In the female inflorescence 

 the archegonia of R. autoica are directed forward and the most 

 conspicuous part of the branch is the lobe-like structure lying in the 

 same plane as the higher axis, the actual wings of the inflorescence 

 being reduced. In R. diversiflora, on the other hand, the arche- 

 gonia are directed upward, no lobe-like structure is developed, and 

 the wings of the inflorescence are well developed and expanded. 



Another species with which R. diversiflora should be com- 

 pared is R. tenerrinia. The two plants are of about the same size, 

 they branch in much the same way, they are both monoicous, and 

 both show very similar histological features. R. diversiflora, 

 however, is a firmer plant than R. tenerrima; rhizoids are far 

 more sparingly produced ; and the contrast in size between the 

 superficial and interior axial cells is more marked. The sexual 

 branches yield characters which are still more distinctive. In 

 R. diversiflora bisexual branches are not uncommon ; the male 

 spikes are about i mm. long and 0.6 mm. broad, and the wing is 

 two or three cells broad ; the female branch is distinct and has 

 numerous archegonia and broad lobate or ciliate wings. In R. 

 tenerrima no bisexual branches have been observed ; the male 

 spikes are usually less than 0.5 mm. in length and only about 0.25 

 mm. in width, and the wing is only one cell wide; the female 

 branches are reduced to very short lobes with only one or two 



