198 ZYGNEMATACEAE 



in which the tubes are similarly formed by the male cell, but the segregation 

 ot reproductive and vegetative cells is not so evident. 



181. Spirogyra prescottii (Prescott) Transeau 1944. Ohio Jour. 



Set. 44, p. 243. Amer. Midland Naturalist. 27, p. 673, 

 PI. 4, Figs. 15-17. 1942 (as S. collinsii var. minor). 



Vegetative cells 13-14/i. x 1 15-140 /i, with plane end walls; i chro- 

 matophore, loosely spiraled; conjugation scalariform; tubes formed by 

 the male gametangia; fertile cells inflated to ^7^ix\ zygospores ovoid to 

 ellipsoid, 29 /^ x 39-40 /a; median spore wall coarsely punctate, yellow. 



United States: Massachusetts, Falmouth, July, 1933. 



The dimensions are so much smaller than those of S. collinsii that it 

 seems better to separate it as a distinct species, although it is certainly very 

 similar in other respects. Named for G. W. Prescott, State College, Mich- 

 igan, author of many publications on fresh-water algae including Algae of 

 Iowa. 



182. Spircx5yra chenii Jao 1935. Sinensia. 6, p. 587, PI. 4, Fig. 52. 



Vegetative cells 19-22 jia x 38-11 5 ju,, with plane end walls; i chro- 

 matophore, making i to 5 turns in the cell; conjugation lateral and 

 scalariform; conjugating tubes formed by the male gametangia; fertile 

 cells inflated up to 42 ju, usually separated by i or more sterile cells; 

 zygospores ellipsoid, 25-32 /u. x 45-61 yu,; median spore wall smooth, yel- 

 low at maturity. (Pi. XXXIII, Fig. 14.) 



China, Szechwan. 



183. Spirogyra collinsii (Lewis) Printz 1927. Engler and Prantl. 



Pflazenfamilien. Second edition, 3, p. 371. Amer. Jour. 

 Bot. 12, p. 351, 1925 (as Temnogyra eoUinsii). 



Vegetative cells 18-22/^ x 100-200/^, with plane end walls; i chro- 

 matophore, rarely 2 in some cells, making from 3 to 9 turns in the cell; 

 conjugation usually lateral, sometimes scalariform; tubes formed mostly 

 by the male gametangia; fertile cells inflated, 25-39 ;u x 45-110 jli; zygo- 

 spores ellipsoid, or sometimes ovoid, 26-37^ x 52-62 (-1 10) )u,; median 

 spore wall coarsely punctate, yellow. (PI. XXXIII, Figs. 12-13.) 



United States: Massachusetts, Woods Hole, July, 1922; Mississippi, 

 Biloxi, February 14, 1934 (Hicks Coll.); Florida, Daytona, March 12, 1931 

 (Tiffany Coll.), and Tarpon Springs, August 7, 1945 (R. K. Salisbury 

 Coll.). 



This species is one of the most specialized of the "punctata group" in 

 that the gametangia are much smaller than the vegetative cells, and most of 

 the chromatophore passes into the gametangial end during cell division, 

 leaving only a small portion in the sterile cell. This remnant is often flat 

 and straight, or only slightly curved, as in Mougtotia. When I first saw 

 the species in the Biloxi collections 1 took it to be a Temnogametum until I 



