88 



surrounding the pores sometimes show thickened radial walls. 

 In the compact ventral tissue, moreover, thick-walled cells 

 with elongated pits are not uncommon, and a number of species 

 are known in which pointed sclerotic cells with pigmented walls 

 can be demonstrated. Of course none of these cells bear much 

 resemblance to the green cells of the Riccia. Perhaps the latter 

 are more directly comparable with the parench3-matous cells 

 found in the costa of Pellia epiphylla (L.) Corda and P. Neesiana 

 (Gottsche) Limpr, Here, as in all the Jungermanniales, the 

 gametotype is destitute of air-spaces, but the interior cells of 

 the thallus show distinct vertical bands of thickening in their 

 longitudinal walls. The bands, which are narrow and often 

 pigmented, undoubtedly serve in a mechanical capacity, and 

 the same thing is probably true of the much longer bands of 

 Riccia histriata. 



According to Stephani* tw^enty-three South American species 

 of Riccia were known in 1898, thirteen belonging to Riccia 

 proper and ten to Ricciella. Not one of these species is accredited 

 to Peru. In 191 1 Weberbauerf was able to report two species 

 from the vicinity of Mollendo, listing them under manuscript 

 names of Stephani. Since these species have not been adequately 

 published, so far as the writer knows, they need not be further 

 considered. Among the species described by Stephani, R. 

 Weinionis Steph., collected by Welnio at Rio de Janeiro, is 

 perhaps the most closely related to R. histriata. In the Brazilian 

 species, however, the spores are smaller, measuring 102 ju in 

 diameter, the inflorescence is described as monoicous, and the 

 dorsal sulcus is not restricted to the apical region. It is unfor- 

 tunate that Stephani makes no allusion to the anatomical features 

 of his species, nothing being said about the epidermis, the green 

 cells, or the compact ventral tissue. 

 Sheffield Scientific School, 

 Yale University 



* Bull. Herb. Boissier 6: 310-343, 361-378. 1898. 

 t Engler & Drude, Vegetat. der Erde 12: 145. 1911. 



