Mar., 1922 classification of plants 135 



7. Valves without a raphe or pseudo-raphe; usually with a concentric or radiating 

 symmetry around a central point, rarely isobilateral or zygomorphic; 

 valve view usually circular; polygonal, or broadly elliptical in outline. 

 Eupodiscales. 



7. Valves with a raphe or pseudo-raphe, or with a sagittal line; with an isobi- 



lateral or zygomorphic symmetry, never centric; valve view mostly boat- 

 shaped, needle-shaped, rod-shaped, or elliptic in outline. Naviculales. 



8. Unicellular or simple free filaments, chlorophyll-green, with complex chro- 



matophores containing prominent pyrenoids, reproduction usually by con- 

 jugation of the cell contents either through a conjugation tube or by the 

 breaking open of the cell walls; cells and gametes never with cilia; 

 unicellular forms usually of fantastic shapes, usually divided into two 

 symmetrical halves. (Conjug.at^). 9. 



8. Sexual process if present by t^-pical isogametes, or heterogamous; plants 



commonly branched filaments or massive, the unicellular forms or simple 

 filaments rarely corresponding to the above description. 10. 



9. Thallus a filament or mostly unicellular, the cell wall usually divided into 



two symmetrical halves, cells mostly constricted at the middle; con- 

 jugation by the breaking open of the cell walls or by the formation of a 

 primitive conjugation tube. Desmidiales. 

 9. Thallus a simple filament of cylindrical cells not constricted in the middle, 

 but sometimes the contents divided into symmetrical halves; these latter 

 forms distinguished from the preceding order by the definite filament 

 and the prominent conjugation tube. Zygnemales. 

 10. Antheridia when present not consisting of a globular structure containing 

 sperm-bearing filaments. 11. 



10. Filamentous green algas with globular antheridia containing sperm-bearing 



filaments, erect, branches in whorls; rhizoids thread-like; sperms biciliate, 

 non-sexual spores absent; plants more or less incrusted with lime. 

 (Ch.\re.«;). Charales. 



—1 I'- 

 ll. Plants green, rarely with a red or brown color and then unicellular; nearly 

 all producing zoospores except the lowest; largely fresh water algae, but 

 some marine. 12. 



11. Plants usually with the chlorophyll hidden by a brown, red, or purple pig- 



ment, always with a multicellular body, often massive; sperms motile or 

 non-motile; mostly marine algas. 29. 



12. Plants unicellular or colonial, not truly filamentous. 13. 



12. Plants filamentous or massive. 18. 



13. Nonsexual unicellular or colonial algae without zoospores, commonly with 



autospores or merely splitting apart; cells normally with one nucleus, not 

 forming net-like or fantastic, radially symmetrical plate-like union colonies 

 (Autospor.'E). 1-4. 



13. Isogamous or heterogamous sexual algae usually with zoospores. 15. 



14. Reproduction by autospores, the protoplast dividing within the mother cell 



and the daughter cells escaping singly or in colonies. Selenastrales. 



14. Reproduction by vegetative division and separation by the splitting apart of 



the daughter cells. Protococcales. 



15. Unicellular or colonial algse with cells normally having one nucleus; the 



colonial forms not produced by the symmetrical aggregation of free 

 zoospores. (Chlorococce.e). 16. 



15. Cenocytic algae consisting of net-like or symmetrical plate-like colonies of 



peculiar form, produced by the definite arrangement and union of daughter 

 cells in the parent cenocyte; (Hydrodictye.e). Hydrodictyales. 



16. Cells ciliated and active in the vegetative state; unicellular or in definite 



colonies, commonly spherical. Volvocales. 



16. Cells not active in the vegetative stage. 17. 



17. Vegetative cell division absent, cells separate or somewhat cenocytic. 



Chlorococcales. 

 17. Colonies increasing by vegetative division. Tetrasporales. 



