1919] Setchell-Gardner : Myxophijceae 5 



The majority of the species whether in filamentous form (as a 

 few of them are) or unicells, or even the non-filamentous colonies, do 

 definitel}" reproduce by vegetative cell division, separating cells which 

 individually are capable of further growth. A few species, particu- 

 larly those of the genus Dennocarpa, have no strictly vegetative 

 method of multiplication, reproducing only by gonidia, j'et in every 

 other way are closely allied to the rest of the genera included under 

 Coccogonales and must, therefore, be placed in this order. 



The order is usually divided into two families, viz., Chrooeoccaceae 

 and Chamaesiphonaceae. 



Key to the Families. 



1. Multiplication by vegetative cell division (coccogonia) or by encysted cells 

 (resting spores) ; strictly non-filamentous Family 1. Chrooeoccaceae (p 5) 



1. Multiplication by vogotativo coll division (coccogonia) and by endogenous gonidia; 

 unicellular, in globular or irregular colonies and, at times, distinctly filamen- 

 tous Family 2. Chamaesiphonaceae (p 20) 



FAMILY 1. CHROOCOCCACEAE naeg. 



Cell solitary or associated into families of indefinite shapes and 

 sizes, free floating or attached ; cell wall usually thin, surrounded by a 

 more or less copious gelatinous or mucilaginous, at times highly 

 colored, tegument; protoplast homogeneous or granular; multiplica- 

 tion wholly by vegetative cell divisions in one, two, or three planes, 

 the cells separating immediately, or remaining in contact for a longer 

 or shorter period of time after which the teguments dissolve and 

 liberate them. 



Naegeli, Gatt. einz. Algen, 1849, p. 44. 



Naegeli, in founding the family Chrooeoccaceae, included some 

 eight genera, all of which, by common agreement, remain within the 

 limits of the family. Later writers added genera some of which have 

 been separated to form the family Chamaesiphonaceae of Borzi. Vari- 

 ous distinctions have been attempted between these two families but 

 it seems to us that the only satisfactory basis, at present at least, is 

 that of the lack of gonidia-formation in the Chrooeoccaceae and its 

 presence in the Chamaesiphonaceae. This was, at least, one of the 

 important distinctions in the mind of Borzi (1882, p. 312). Later 

 writers have found difficulties in this (cf. "West, 1916, p. 41) because 

 of possibly greater prevalence of gonidia-formation among members 

 of the Myxophyceae than had been previously described. Some of 

 the described cases, however, must, as it seems to us, be more definitely 



