112 



THE AMERICAI^^ MONTHLY 



[June, 



a. Genera with only asexual propa- 

 gation. 



b. Genera with sexual pi'opagation. 

 In making this convenient division, it 

 should be understood that the distinc- 

 tion is not regarded by the present 

 writer as having the slighest perma- 

 nent value. It will be observed that 

 as here used the term sexual propa- 

 gation applies only to propagation by 

 means of male and female cells, the 

 former (antheridia) giving rise to 

 spermatozoids ; the latter to oogonia, 

 which are fertilized by the spermato- 

 zoids. 



It by no means follows that this is 

 the only process of sexual propaga- 

 tion among these algaj. It may be 

 said, and with considerable reason, 

 that the conjugation and fusing to- 

 gether of microgonidia, as in the 

 genus Chlaniydomonas ^ for example, 

 is a true sexual process ; indeed, we 

 have so designated it in several in- 

 stances, for want of a better term. 

 Nevertheless, we are rather inclined 

 to regard this process as a sort of 

 parthenogenesis, although there are 

 observations which tend strongly 

 toward a different view. 



A. — Propagation Asexual. 



Families of spherical or t^ibular 

 form ; in some cases the cells of the 

 family separate from each other and 

 each one swims free, like swarm- 

 spores of the confervas. 



Propagation by pairing of the 

 swarm-cells, or asexual by partheno- 

 gonidia or unsexual swarm -cells. 

 The copulation of the swarm-spores 

 has been certainly observed in two 

 genera, but in some other genera 

 swarm-spores of two kinds, macro- 

 and microgonidia have been seen, 

 which indicate a not yet obs'ei-ved 

 copulation of the micro-gonidia. 



Synopsis of Genera. 



Cells single, motile. 



Green, centre red, envelope 

 widely extended from plasma. 

 Chlamydococcus^ 45. 

 Green, envelope close. 



Chlamydomonas.^ 46. 



Cells in motile families. 



Family spherical , 8 spindle-shape 

 cells in hyaline sphere. 



Stephanosphcera^ 47. 

 Family flat or tabular, 4-16 cells 

 in hyaline envelope. 



Goniutn., 48. 

 Family spherical, cells brown- 

 ish, wedge-shape, 2-32 in 

 berry-like mass, within hya- 

 line envelope. Synura, 49. 

 Family spherical, cells angular, 

 in berry-like mass, within 

 hyaline envelope. 



Pandoriiia^ 50. 

 Genus of doubtful value omitted. 



Spondyloniorum. 



45. Genus Chlamydococcus A. 

 Braun. 



Families do not remain united after 

 their growth from one mother-cell,* 

 but the individual cells (macrogo- 

 nidia) separate. These are spheri- 

 cal, covered with a cellulose mem- 

 brane, which is commonly somewhat 

 widely separated from the plasma 

 (mantel-like), with green, in the 

 middle red, contents, the anterior end 

 colorless, pointed, with 2 flagella ; 

 the plasma-body usually attaclied to 

 the membrane by gelatinous exten- 

 sions. 



Sexual propagation unknown. 



Asexual multiplication of t w o 

 kinds : — i . By macrogonidia 2-4—8 

 from a mothei'-cell, which come to 

 rest and after a period of dryness 

 divide into 2-8 swarm-cells, with 2 

 flagella. 2. By repeated division of 

 one mother-cell a large number of 

 microgonidia are formed, with 2 cilia, 

 of red or dull green color and with a 

 red spot. These (perhaps after copu- 

 lation) come to rest. 



[The so-called red snow , commonly 

 known as Protococcus nivalis or Hce- 

 niatococcus nivalis^ is now placed 

 in this genus as Chlamydococcus 

 nivalis.^ 



46. Genus Chlamydomonas Ehren- 

 berg. 



Families do not remain united, but 

 the individual cells separate. These 

 (macrogonidia) are similiar to those 



