1920] Setchell-Gardrier : Phycologieal Contributions 289 



In connection with cross-sections of Prasiola mexicana, it may be 

 said that the various specimens agree very well as to the number and 

 arrangement of cells but differ somewhat in width of section. In 

 width the sections vary from 24/x to 52/x, but the increase in thickness 

 is more or less associated with the development of the so-called aplauo- 

 spores. "We find these arising in greater numbers from a single cell 

 than any description thus far indicates for any species of Prasiola. 

 Lagerheim has described and figured them for Prasiola mexicana var. 

 quitensis Lagerheim (1892, pp. 370-372, pi. 20, figs. 15-22) . He found 

 either a single layer of tetrads {loc. cit., fig. 18) or two layers of tetrads 

 (loc. cit., fig. 20) in the membranes of his variety. In our specimens 

 we find the double row of tetrads (cf. pi. 21, figs. 3-7), and also double 

 rows of tetrads intermingled with groups where the horizontal divisions 

 have proceeded farther, as they do in antheridial formation in certain 

 species of Porphyra. The majority of sections show the two kinds 

 (or stages in development) of these bodies intermingled. We feel it 

 necessary to consider these bodies as aplanospores until further investi- 

 gation can shed more light as to their fate, but the resemblance 

 between them and the species of Porphyra, as well as the resemblances 

 in cell structure, particularly as regards the shape and position of 

 the chromatophore, suggests strongly the possibility of a nearer re- 

 lation to the Bangiales than to the Ulvales and a remote ( ?) possibility 

 that we may be dealing here with antheridia and a very simple type 

 of cystocarp. 



Comparing our specimens with the descriptions and figures of 

 Agardh and Jessen, we believe them to be true Prasiola mexicana, and 

 comparing them with Lagerheim 's descriptions and figures we are 

 inclined to agree with him that the Equador plant is different, possibly 

 even specifically. 



One of us (Setchell) has found a Prasiola in Crane Creek (Mari- 

 posa County, California), between Big Meadow and MeCauley's, which 

 differs so much from P. mexicana that it seems desirable to describe 

 it as new. It diff'ers from P. mexicana in habit, color, and structure. 

 It is always elongated (cf. pi. 21, figs. 11-13), while P. mexicana is 

 broad and umbilicate. In color it is light, almost yellow-green, instead 

 of the darker green characteristic of P. mexicana. In surface view 

 (cf. pi. 21, figs. 14^16) the smaller groups of cells are more distinctly 

 placed and are further marked off into areas by delicate lines (or 

 borders) in the enclosing jelly. The sections (cf. pi. 21, figs. 17, 18) 

 are as broad as the narrower sections of P. mexicana, being 11 fj. to 25ju, 



