58 SPECIES OF ALG^E. 



aa. Cells more than 100/4 in diameter (bb). 

 aa. " from 72 to 100/4 " (cc). 



aa. " less than 70/4 " " (dd). 



bb. Cells 150-156/4 in diameter (the largest species) . . crassa, 219 



bb. il 102-110 /.i " " setiformis, 219 



cc. Cells 90-100/4 in diameter jugalis, 219 



cc. " 72-78/4 " " 1-3 times as long as wide nitida; 217 



^. " 75/4 2-4 " " " " " parvispora, 221 



dd. Cells 58-65/4 " " orthospira, 218 



dd. " 33-38/4 " " fluviatilis, 216 



*?<?. Cells 65-78/4 in diameter &?//*>, 217 



<?<?. " 58-65^ " " orthospira, 218 



_//". Filaments of two diameters, one i25//, the other 8o/*, 



in&qualis\ 218 



ff. " " same diameter, 150-156^ crassa, 219 



//. " " " " 102-11 o/i . . . setiformis, 219 



ff. " " " " 118-125/4 .... maxima, 218 



^7". " " " " 54-62^ majuscula^ 221 



gg. Cells 4-10 times as long as broad, 24-27/4 diam. . mirabile, 211 

 . " 2-12 " " " " " 25-30/4 diam. . longata, 214 



II. KEY TO FERTILE FILAMENTS OF SPIROGYRA. 



For method of determining the number of bands in the cell, see the 



Key to the sterile filaments of Spirogyra, p. 56 

 Cell membrane folded in at the ends (a). 

 " " not folded in at the ends (/). 



a. Chlorophyll band single, rarely double (b). 



a. " two or more (//). 



b. Membrane of spore smooth (r). 



b. " " " punctate (g). 



c. Spores elliptical or fusiform (d). 



c. " ovate or oval (e). 



d. Spore 24-30/4 by 50-58/4 tenuissima, 207 



d- " 3~36/< in dia., twice as long inflata, 207 



d. " 27-32/4 in dia., 2-4 times as long .... quadrata, 208 

 t. Spore-bearing cells inflated (/). 



<?. " " " slightly dilated; spore 26-30/4 in dia., 



Weberi, 208 



f. Spores 36/4 in diam., 2-3 times as long as wide . Spretiana, 208 



f- " 3-36/< in diam., 2-2% " " " " . Grevillcana, 209 



