PALMELLA. 307 



form, therefore, of the frond is necessarily indefinite. By 

 reason of the absence of the vesicles nourished in the interior 

 of the larger globules, the material included in the globules 

 is altogether continuous, fluid, and never granular. At length, 

 when effused, the presence of dots or minute granules dis- 

 persed through the mucous substratum afford distinct cha- 

 racters whereby the genus may be easily distinguished by 

 microscopic examination. 



In the genus Palmella, as limited by himself, Meneghini 

 describes two species, Palmetto, cruenta and P. montana. 

 The first of these Meneghini takes for the type of his genus 

 Palmetto,, and to this only do his observations in any mea- 

 sure apply. The other species seems to me to be of a nature 

 altogether different, indeed scarcely congeneric. In P. cruenta 

 the grains or cells are loosely scattered through the mucous 

 matrix, and their contents are usually, as Meneghini describes 

 them, uniform and homogeneous. In P. montana, P. Ralfsii, 

 P. virescens, and P. grumosa, the cells are collected into little 

 clusters, and their contents are nucleated. Meneghini, there- 

 fore, would not appear to have studied the second species of 

 his genus P. montana, which, as well as the other species 

 Palmetta Ralfsii, P. virescens, and P. grumosa, ought, in all 

 probability, to be included in a distinct genus. Palmetta cruenta, 

 on the one side, evidently bears a close relation to Protococcus 

 nivalis, from which indeed it principally differs in the fact 

 of the globules being distinctly immersed in gelatine, while 

 in P. nivalis they are free. P. montana, &c., on the other 

 hand, exhibits a relation almost as close to Hcematococcus, from 

 which genus it differs in the same manner as Protococcus 

 nivalis and Palmetta cruenta differ. The globules of ffcema- 

 tococcus sanguineus exhibit the same nucleated appearance as 

 do those of P. montana, P. Ralfsii, &c. 



x 2 



