8 University of California Puhlications in Botany [Vol.8 



The species of Syncchococcus are to be distinguished from one 

 another by their diameters and bj^ the relation of proportion between 

 these and their U'ligths. The present species is of intermediate diam- 

 eter as these range among the species of the genus, and very short in 

 proportion. Some of the cells approach spherical and consequently 

 resemble Synechocystis, but the majority are at least somewhat longer 

 than broad even in stages just succeeding division. 



3. Merismopedia ]\Ieyen 



Cells spherical, or narrow ellipsoidal, with thin cell walls, and firm, 

 hyaline, structureless teguments becoming dififluent and binding the 

 cells together; division regularl}^ in two planes, building up colonies, 

 at first square, or regularly rectangular, later often irregular in 

 outline through injury or failure of certain cells to continue division. 



Meyen, Wiegman's Arch. f. Naturgesch., Jahrg. 5, vol. 2, 1839, 

 p. 67 {nomen nudum); Kuetzing, Phyc. Gen., 1843, p. 163 (descr.). 

 Gonidium Ehrenb., Infusionsth., 1838, p. 59 {nomen nudum) ; Mene- 

 ghini, Syn. Desm. hue Cog., 1840, p. 213 (descr.). Agmenellum de 

 Brebisson, De quelq. nouv. genres d'Alg., 1839 (May), p. 2, Diet, 

 univ. d'hist. nat., vol. 1, 1841, p. 187; Trevisan, Prospetto della Flor. 

 Eug., 1842. 



The plants which have passed undisputedly under the name of 

 Merismopedia for so many decades form a well defined and recog- 

 nizable generic unit. When the historj^ of the name is investigated, 

 it is found, unfortunateh', to possess no valid status. Merismopedia 

 was used by Meyen simply as part of a binomial and with no definite 

 diagnosis in 1839, and was probably published comparatively late in 

 the year. It seems, therefore, to be a nomen nudum. It was first 

 accompanied by a proper diagnosis in Kuetzing 's Phycologia gcneralis 

 in 1843. In the meantime two other names were suggested, Gonidium 

 by Ehrenberg and Agmenellum- bj'- de Brebisson. The name Gonidium 

 is also to be held as a nomen nudum since it was used by Ehrenberg 

 as a subgeneric designation under Gonium. He remarks (1838, p. 59), 

 however, that he would, if he understood the plants better, place both 

 Gonium tranquillum and G. glaucum in a new genus Gonidium, but 

 he prefers to leave them under Gonium. In 1840 Meneghini took up 

 and described Gonidium as a genus, on the ground, as he distinctly 

 states, that it antedated the genus Agmenellum of de Brebisson. 



