THE GREEN ALGAE OF NORTH AMERICA 239 



ful examination should be easily distinguished by the dotted, 

 not continuous " meridians" on the spore. 



23. OE. CRENULATO-COSTATUM Wittrock, 1878, p. 139; 



Hirn, 1900, p. 129, PI. XV, fig. 84; P. B.-A., Nos. 810, 1426. 

 Dioecious; oogonia single or 2-3, rarely 4-5, oboviform or 

 subellipsoid, rarely oblong-ellipsoid, pore superior; oospore 

 same form as the oogonium, filling or nearly filling the latter, 

 membrane triple, external membrane smooth, median mem- 

 brane with 14-20 longitudinal, crenulate, sometimes anastomos- 

 ing lines ; male plant somewhat more slender than the female ; 

 autheridia 2-6-celled, often alternating with vegetative cells ; 

 spermatozoids binate, division horizontal ; terminal cell, which 

 not infrequently is an oogonium, obtuse or short-apiculate. 



veg. cell, female, 10-18 /u. diatn., 2^-7 diam. long. 



veg. cell, male, 9-13 M " 3>-6 " 



oog., 30-36 M " 40-65 M long. 



oos., 28-34 M " 37-55 V- " 



anth. cell, 9-12 M " 9-14 M " 



Mass., Conn., N. Y., Pa. 



Forma CYLINDRICUM Hirn, 1900, p. 129, PI. XV, fig. 85 ; 

 P. B.-A., No. 118, as Oe. Bosrii. Ooogonia and oospores of 

 variable form, generally cylindric-oblong, rarely ellipsoid or 

 obovate-ellipsoid ; longitudinal lines slightly crenate or almost 

 entire ; oogonia single or 2-4 ; vegetative cells slender. 



veg. cell, 11-16 n diam., 4-10 diam. long. 



oog., 30-36 M " 42-81 M long. 



oos., 2 7-34 M " 40-65 /j. " 



Mass., Conn., Mo. 



Var. AUREUM Tilden, Amer. Algae, No. 123; 1898, p. 90, 

 PI. VIII, fig. 1-3 ; Hirn, 1900, p. 130, PI. XV, fig. 87. Slender, 

 oogonia shorter than in the type, single or 2-3 ; oospore obovoid 

 to globose-ellipsoid, not quite filling the oogonium ; lines of the 

 oospore only scantily toothed, connected by distinct cross-lines. 



veg. cell, 10-13 M diam., 3/^-9 diam. long. 



oog., 3-35 M " 38-50 M long. 



oos., 29-33 M " 35-43 P " 



In warm water, Yellowstone National Park. 



The peculiar character of the "meridians" identifies this 

 species in its various forms, much as the latter differ in other 

 particulars. Hirn thinks it probable that under this name 

 should be included Oe. apiculatum Wolle, 18773, p. 188. 



24. OE. TAPiiROSroRUM Nordstedt and Hirn in Hirn, 1900, 



