Grinnellia americana, Harv. 7 



possible to demonstrate that open communication for inter- 

 change of nuclei, chromatophores, and other protoplasmic 

 products between adjacent vegetative cells is established by 

 these pits. In Schmitz's discussion of them he says they are 

 traversed by plasma-cords which serve for conduction of 

 dynamic influences from cell to cell. He thinks that a transfer 

 of dissolved food-material from cell to cell is facilitated because 

 of the pores in the separating membrane of the pit, but that 

 migration of protoplasm by means of these open communi- 

 cations is inadmissible. He further states that open com- 

 munication between cells of Algae is rare, and that when 

 formed, as in Corallineae, the pores result from the subsequent 

 modification of the common dissepiment of adjacent thallus- 

 cells. 



His views regarding the pits between thallus-cells of Algae 

 are evidently correct with reference to the organic connexion 

 of the cells of Grinnellia, with one exception — the con- 

 nexion between the procarpic cells. As will be seen in the 

 discussion of the procarp, the procarpic cells are connected, 

 not by pits, but by open pores, which are established, possibly, 

 in the manner ascribed by him to Corallineae. 



Physiology. 



Plants were found growing on the outer surface of the outer- 

 most piles of wharves at Nantucket and Woods Hole, having 

 an eastern, southern, and western exposure to sunlight ; while 

 very few plants were found on the exposed surface of the 

 north piles. Whether this was due to lack of light can hardly 

 be stated, as other conditions, decidedly unfavourable to 

 growth, were present. Not a single plant was found on the 

 inside of outer piles nor on the outside of piles in any great 

 degree shaded, while several other Algae belonging to the 

 groups of the Chlorophyceae and Rhodophyceae were dis- 

 covered growing in these places. This indicates that Grin- 

 nellia is far more dependent upon light than many of the 

 Algae associated with it. 



