462 University of California Publications in Botany [Vol. 6 



bear naming it at present. Howe (1914, p. 12) states that he is unable 

 to find in Miss Tilden's distribution, mentioned above, any member of 

 the Chlorophyceae that he could interpret as being her Pringsheimia 

 scutata forma Cladopliorae, under which name no. 382 was distributed, 

 but suggested that possibly the species referred to was that of a 

 Dermocarpa, thus indicating that genus as being present in the mate- 

 rial he examined. By far the most abundant species present in Pro- 

 fessor Setchell's material is no one of these but is the plant described 

 above. Some specimens of the host are much contorted by its pres- 

 ence. This species seems most likely to be the one upon which was 

 based Pringsheimia scutata forma Cladopliorae, and is the plant, in 

 part at least, later described and figured as Chlorogloea tuberculosa 

 by Miss Tilden (Minn. Alg., 1910, p. 46, pi. 2, fig. 42). 



Xenococcus Gilkeyae Setchell et Gardner sp. nov. 

 Plate 39, fig. 11 



Cellulis solitariis aut in colonias parvas consociatis, solitariis, 

 sphaericis, sed in coloniis angulatis et plus minusve elongatis, 4-7 /x 

 raro 9/* diam. ; parietibus inconspicuis, hyalinis ; cytioplasmate dilute 

 coeruleo-viridi ; gonidangiis cellulis vegetativis forma magnitudine- 

 que similibus; gonidiis 0.8-1/^ diam., divisionibus iteratis formatis. 



Cells solitary or aggregated into small colonies, spherical when 

 solitary, angular and more or less elongated in colonies, 4— 7/x, rarely 

 9//, diam. ; cell wall inconspicuous, hyaline ; protoplast light blue- 

 green; gonidangia of the same shape and size as the cells; gonidia 

 0.8-lju. diam., formed by successive divisions of the protoplast. 



Growing on the filaments of Elachistea sp. which is epiphytic on 

 Fucus sp. Lower littoral belt. Sitka. Alaska. Type no. 3962a, 

 Gardner. 



Having vegetative cell divisions in but two planes perpendicular 

 to the substratum, Xenococcus Gilkeyae is a typical Xenococcus. It 

 is an exceedingly delicate species but the type material being in 

 excellent vegetative and reproductive conditions is clearly definable. 

 The gonidia appear to be the results of two lines of development of the 

 vegetative cells. Some gonidia seem not to divide vegetatively after 

 coming to rest, but continue to increase in size until maturity is 

 reached, then by a few successive internal divisions the whole proto- 

 plast is progressively converted into gonidia. In some cases the first 

 division takes place horizontally, cutting off a small portion of the 

 base of' the protoplast, which in some instances seems to remain sterile, 

 at least the whole upper part is converted into gonidia before the 



