58 SPECIES OF ALG^E. 



aa. Cells more than loo/^ in diameter (bV). 

 aa. " from 72 to loo^u " " (cc). 



aa. " less than 70/t " " (id), 



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



bb. " 102-iioyW " " setiformis, 219 



cc. Cells 90-1 00/t in diameter . . Jugalis, 219 



cc. " ■j2-'j8jA " " 1-3 times as long as wide nitida; 217 



cc. " 75// " " 2-4 " " " ' 



dd. Cells 58-65/^ " " 



ee. Cells 65-78/^ in diameter 



^c. • " 58-65/* " " 



7y. Filaments of two diameters, one 125//, the other 80/^, 



incequalis, 218 

 jy. " " same diameter, i5o-i56/( 



//". " " " " 102-iiOyU 



^. " " " " 1 18-125// 



//. " " " " 54-62/^ 



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

 gg. " 2-12 " " " " " 25-30/4 diam. 



parvispora, 221 



orthospira^ 218 



fluviatilis, 216 



be His, 217 



ortkospira, 218 



. crassa, 219 



setiformis, 219 



maxima, 218 



tnajuscula, 221 



mirabile, 211 



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 ((z). 

 § " " not folded in at the ends (7). 



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



a. " " two or more {K). 



b. Membrane of spore smooth (c). 



b. " " " punctate {g). 



c. Spores elliptical or fusiform (d'). 



c. " ovate or oval (e). 



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

 '^- " 3°-36/< in dia., twice as long . . inflata, 207 



d. " 27-32/t in dia., 2-4 times as long . . quadrata, 2c8 

 <?. Spore-bearing cells inflated (/). 



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



Weberi, 208 



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

 f- " 30-36/t in diam., 2-2 J4 " " " " . Grevilleana, 209 



