1919] Setchell-Gardncr : Myxophyceae 35 



5. Xenococcus Chaetomorphae S. and G. 

 Plate 2, ligs. 2-i 



Vegetative cells extremely variable in shape and size, some spherical, 

 some very angular and of nearly equal dimensions, and some long and 

 narrow, tapering to sharp points at both ends as seen from above, 

 up to 25/A in vertical diameter, tlic narrower cells up to 45/a long; 

 gonidangia the same shape as the vegetative cells ; gonidia formed by 

 successive divisions of the whole protoplast; color bright blue-green. 



Growing on Chaetomorplia acrea in a pool near high-tide limit. 

 Cypress Point, IMonterey County, California. 



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

 p. 436, pi. 36, figs. 2^. 



This species was found associated with Dermocarpa pacifica, and it 

 is somewhat difficult to distinguish the two species. Both species 

 produce gonidia in great abundance, and plants of both species may 

 be found in all stages of growth at the same time. They are very 

 abundant, intermingled, and as seen from above are very angular 

 on account of lateral pressure resulting from growth. There appears 

 certainly to be vegetative growth in the Xenococcus, as the continuous 

 areas covered by it, comprising many hundreds of cells, seem far too 

 great to have arisen from a single group of gonidia; also should tjie 

 gonidia escape singly they could never by chance become so uniformly 

 and closely associated as they often are to be found. The cells of 

 Xenococcus in all stages of growth are extremely angular and very 

 variable in shape and size ; sometimes being much crowded at the 

 cross walls of the host plant, the tendency is to elongate vertically. 

 Frequently groups of cells seem to have started to grow on the cell 

 walls of young cells of the host between the cross-walls, and as the 

 host coll elongates the cells of the epiphyte seem to elongate abnor- 

 mally ill the direction of the long diameter of the host (pi. 2, fig. 2). 

 There are no particular shapes and sizes of gonidangia, since any of 

 the long narrow cells, small angular cells, or large spherical cells may 

 be transformed into gonidangia. The gonidia are formed by suc- 

 cessive divisions of the whole of the protopla.st (pi. 2, fig. 4). On 

 the whole, it seems almost certain that we have here two plants of 

 different genera closely and intimately associated, and it certainly is 

 not possible to distinguish the individuals of the two in all stages of 

 their development. 



