1919] Setchell-Gardner : Myxophyceae 19 



cell walls hyaline ; cell contents pale .yellowish green, homogeneous. 



Growing on the stipitate portion of Iridaea minor J. Ag. in the 

 lower littoral belt. Carmel Bay, Monterey County, California. May, 

 1916. 



Setchell and Gardner, in Gardner, New Pac. Coast Alg. 11, 1918, 



p. 434, pi. 36, fig. 1. 



Just where to align a plant like Chlorogloea lutea is a problem 

 more or less perplexing. It starts to develop on the surface of the 

 host plant, and if the cuticle of the host is sound in that particular 

 place, it developes a dense mass of cells of considerable dimensions 

 before penetrating into the interior. The plant at first spreads out 

 over the host by cell divisions in two or more planes. It is impossible 

 to state the size of a single plant or colony, for in some places on the 

 host it is continuous for several millimeters. This may, however, be 

 due to the coalescence of several colonies. Later cell divisions in the 

 horizontal plane increase the mass in thickness, up to lOOju, or more. 

 At first the cells are arranged in vertical rows, but soon this arrange- 

 ment is destroyed by false branching or by divisions in other planes. 

 The cells are mostly quadrate in this mass, being somewhat spherical 

 in its outer portion. Sooner or later at various points from the under- 

 side of the horizontal layer certain cells are able to penetrate through 

 the cuticle and make their way among the cortical filaments of the 

 host. These penetrating filaments branch. The terminal cells become 

 two or more times as long as the other cells. Growth in length of these 

 filaments is apical. Enlargement of the cells back of the growing 

 points, and divisions in other planes soon produce groups of cells 

 which, encroaching on one another, form a solid mass, the cortical 

 cells of the host at times completely disappearing from the area which 

 they occupy. Plants penetrate to a depth of 200|U,. 



Chlorogloea lutea very closely resembles in some ways, particularly 

 in its method of development within the host, Ilyella socialis found 

 growing with it, and also described below. The method of behavior 

 of l)otli within the host is the same. We have not, however, seen 

 H. socialis extending beyond the surface of the host as C. lutea does. 

 H. socialis thus appears to be wholly endophytic, although, on account 

 of the absence of gonidia, we consider the plants in this collection to 

 be immature, and we are unable to say positively what might have 

 developed later. 



The habitat and method of development of Ilyella socialis are 

 so similar to those of Ilyella endophytica Borgesen (1902, p. 525), 



