AN ANALYTICAL KEY 

 TO THE GENERA 



Genera that are to be expected to occur in our region but have so far not 

 been reported there are indicated by asterisks. ( See also Note 2, page 92. ) 



1. Plants macroscopic, 5— iOcm. high, growing erect from rhizoidal 

 attaching organs and showing stem-like branches with inter- 

 nodes and nodes from which whorls of 'leaves' arise (Pi. 79, 

 Fig. 1 ) ; not inclosed in mucilage Characeae 170 



1. Plants smaller, mostly microscopic, if macroscopic and showing 

 whorls of branches, inclosed in copious, sometimes firm, muci- 

 lage - 2 



2. Cells with pigments confined to 1 or more definite chloroplasts 



or chromatophores^ — - — - — 3 



2. Cells with pigments diffused throughout the protoplast (some- 

 times more dense in the peripheral region) -252 



3. Chloroplasts grass-green, chlorophyll predominating; plants form- 

 ing starch or paramylon as a reserve food (starch-iodine test 



usually positive ) - ** 



(Cf. Euglena, Sphaerella, and Trentepohlia, which may have 



green chloroplasts masked by red pigment. ) 



3. Chloroplasts or chromatophores some color other than grass- 

 green, or with green masked by presence of other pigments; food 

 reserve mostly oil or glycogen; carbohydrates not stained blue 



by iodine 1 ' ^ 



( cf . the motile unicell Cryptomonas, however ) 



4. Plants unicellular, solitary (See Desmids: Appendix) 5 



4. Plants not solitary imicells --- - 12 



5. Cells motile in the vegetative state (sometimes non-motile in 

 microscope mounts, with organs of locomotion obscure)-— - — - 6 



5. Cells non-motile in the vegetative state -— 81 



6. Cells with numerous small, green, ovoid chromatophores; food 

 reserve paramylon or oil; swimming by means of 1 or 2 long, 

 whip-Uke flagella (Pi. 86, Figs. 1, 8.) 172 



6. Cells with 1 plate-like, cup- or star-shaped chloroplast; food re- 

 serve starch; swimming by 2 or 4 short flagella (PI. 1, Figs. 3, 17.)- 7 



7. Flagella 2 — - 8 



7. Flagella 4 — - -- H 



8. Cells ovoid to ellipsoid, with the protoplast situated at some 

 distance within the cell wall and connected to it by radiating 

 protoplasmic strands; chloroplast often masked by a red pig- 

 ment ( haematochrome ) Sphaerella (in part) 



8. Cells with or without a gelatinous sheath but without protoplas- 

 mic strands connecting the protoplast to the cell wall 9 



*See Trachelomonas and Dinobryon; species are identiiied by shape and markings of brown 

 or colorless empty tests or loricas. 



[571] 



