The Plankton Algae of the Palisades Interstate Park 137 



The behavior of the two species when mounted under a cover glass 

 is also quite different since colonies of 6". Adamsii begin to dissociate 

 into individual cells almost as soon as they are mounted. Colonies of 

 6'. uvella, on the other hand, do not break down readily. 



Errerella bornhemiensis Conrad. PL 9, Figs. 3-4. 

 Bull. Soc. Roy. de Bot. de Belgique 52: 242, text figs. 1-3. 1913. 



Nigger Pond (rr), Portage Lake (rrr). 



This remarkable alga has not been noted since its discovery by 

 Conrad. It is very closely related to Micractinium but differs in the 

 cellular arrangement and the single long spine on certain of the 

 exterior cells. 



Conrad states that the colony consists of a solid pyramid of six- 

 teen cells. In the specimens that I have observed the unit of 

 structure is in reality a pyramid of four cells which, in turn, is 

 grouped with three other units to form^ a pyramid of sixteen cells. 

 In this sixteen-celled pyramid there is an open space at the center. 

 Isolated sixteen-celled colonies were found but in the majority of 

 cases development had extended to a point where four such sixteen- 

 celled colonies were joined to form a pyramid that contained sixty- 

 four cells. In one case four of these sixty-four-celled colonies were 

 joined to form a pyramidal colony of 256 cells. This colony has been 

 drawn in basal view to show the pyramidal arrangement to better 

 advantage (Fig. 3). 



The cells of the New York specimens are somewhat smaller than 

 Conrad describes, the diameter varying from 3-6 fi. The chloroplast 

 is cup-shaped, but the hyaline portion of the protoplast is opposite 

 and not away from the single spine. As in the Belgian specimens 

 those from New York have no pyrenoids, but this presence or absence 

 of pyrenoids is a matter of minor importance. 



Conrad was unable to find stages of reproduction and so suggests 

 that reproduction may either be by zoospores as in P ediastrum or by 

 autocolonies. Small pyramidal colonies of four cells still enclosed by 

 the old cell wall were observed in the plankton of Nigger Lake. This 

 gives every reason for supposing, therefore, that reproduction is by 

 autocolonies as in the closely related Micractinium. 



Pachycladon gen. nov. 



Cells solitary, spherical, with a delicate cell wall that is without a 

 gelatinous envelope. Cell wall bearing four quadrately (very rarely 

 pyramidately) arranged appendages. Appendages dark brown in 

 color, stout, gradually tapering to a blunt point that is usually bifur- 

 cate. Base of appendages dilate at point of juncture with the cell 

 wall. Chloroplast single, cup-shaped, parietal, nearly filling the cell 

 cavity; with one pyrenoid. 



Reproduction unknowm. 



Pachycladon umbrinus sp. nov. PI. 9, Figs. 5-7. 



Characters as above. 



Diameter of cells without processes 8.5-12.5 fx, with processes 84- 

 112 fx. Length of processes 35-50 ^; breadth of processes at base 

 2-.5-3.75 Ai, at apex 1.0-2.0 ix. 



Little Dam Pond Trr), Nigger Pond (rr). 



