

i n; 



W. B. TURNÉ R, FRESI1-WATER ALG/E OF EAST IN DT A. 



Parvum; lateribus cellularum acute divergente dehtatis, profunde incisis; apicibus 

 forarainatis, partibus exterioribus (c. processubus munitis) tribus conjunctis. 



Long. 10—13, lat. 20 //. G. C. W. 1. c. 

 c. Brcbissonii? Kutz. (Spec. Alg. p. 190, 1849; 1). S/rartzii Bréb. Alg. Fal. t. II, sec. 

 Kutz.; Ehrb. Infus. t. X, f. 8!) Forma ad ha?c accedeus. 



Long. 14—17, lat. 29—81, lat. ap. 24—26 ,«. T. XIX, f. 7. 



The latter exhibits an inclination to the truncate form, but it is not so decided 

 as in Ehrenbergs figure; cfr Wolle, Desm. IT. S. A., t. II, f. 1; also Rabenhorst, 

 Bacill. Sachsens, t, III, f. 41. 



Dr. Wallioh evidently himself saw the typical (large) form foraminated, as 

 appears by bis sketch of 7 Oct. 1855, which, as it was the first delineation of the 

 true conjugation of D. Sivartzii, I have reproduced in facsimile. He says, »showing 

 how two filaments of Desmidium unite to form the broad ragged-looking sporangial 

 filament. The sporangial cells are full of endochrome, whilst the joints are empty or 

 nearly so. * * exhibit the union of the opposing cells just taking place, the fusion 

 occuring by the contents being thrown out and meeting. The upper part exhibits the 

 throwing-out of the cell-contents in the upper filament, without any reciprocal process 

 occuring in the lower one, approximation in the cells not having as yet been suffi- 

 ciently advanced», G. C. \V., Mscr. No. 77; T. XIX, f. 8. 



The copulation of D. Swartzii was noted by the illustrations author of the spe- 

 cies in t. 491, f. 3, Svensk. Bot.; and in the same year (1812) in Disp. Alg. Suee. 

 III, p. 34, he says »post copulationem ad utrumque marginem solutis»! It remained 

 however for Wallich, in 1860, to describe the actual process: »The filaments engaged 

 are invariably placed parallel to each other, and although cells here and there appear 

 to be abortive, the entire number for which there are pairs gradually become fused 

 together. . . . The process takés place in the following order. From the base of one 

 of the constrictions a minute sac is protruded. As it extends in size, the adjacent 

 lobes are pushed widely asuhder, the proximate angles become turgid, and the endo- 

 chrome, which has become condensed at this point, is gradually pourcd into the sac. 

 The already conjugated cells are kept asunder by their enclosed sporangia, at a dis- 

 tance nearly equal to the diameter of the filament. The elongated sacs at first siin}4y 

 impinge upon each other. Shortly, however, they become incorporated, the interposed 

 portion of double cell-Avall is absorbed, the contents of the opposed joints coalesce, 

 and form the large oblong or circular sporangial bodies which wc find occupying the 

 enlarged common cavities between the two conjugated filaments. Lastly, the sporangia 

 remain for a time encysted as just described, but eventually the common cell-wall 

 becomes either broken up or absorbed, the sporangium is invested with its own proper 

 tunics, and, separating entirely from the parent filaments, it wanders forth on its own 

 peculiar reproduetive mission», G. C. W., Desm. Beng. pp. 190, 191. 



The zygospores, like the European ones, are oval, and are 35 X 30 ,« in their 

 diameters. 



The type form is to be met with both having and also wanting the oval fora- 





mina upon 



whi 



ch alone the ffeniis 



. Iptog 



i ni mil w; 



as founded by Ralfs for the conge- 





