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THE GKNUS CHLOIiOCHYTRIUM. 



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completely destitute of the cellulose protuberance so characteristic of tlie 

 cells growing just below the epidermis*. 



Again, much stress has boeu laid upon the form and si/e of the chromato- 

 phore, Reinhardt using these chanicters as the basis of his new genus 

 Chlorocifstls. Moore f and Gardner | have shown, however, that in the species 

 they have examined the shape and extent of the chromatophore vary very 

 considerably in the same individual at different stages of its existence; tlie 

 same is true to a certain degree for Chlorochjtrium grande and for the two 

 species investigated in this paper. 



Further, specific distinction has been made on the basis that in some cases 

 the zoogonidia fuse to form zygotes, while in others they develop asexually 

 without any such fusion taking place. In C. Limnanthemnm, however, 

 Cunningham has observed § that though as a general rule the zoogonidia 

 fuse to form zygotes, yet if fusion does not take place, the zoogonidia are 

 able to develop asexuidly in exactly the same manner as do the zygotes. 

 The same condition has been recorded for other nearly related forms, showing 

 that in these lower algas the fusion of exactly similar zoogonidia cannot be 

 regarded as a true sexual fusion, but only as a case of gamogcnesis. Hen_ 

 the separation into different species of two alga^ which differas to the fusion 

 of their zoogonidia but agree in all other particulars, can only be regarded 

 as an unnecessary multiplication of names of no real value. 



Considerations of this kind have been kept constantly in mind in revising 

 the arrangement of the species of Chlorocliytrium, and with their help it has 

 been possible in certain cases to reduce the number of species. It is very 

 noticeable that whereas certain of the described species stand out as bein- 

 quite different from the rest, yet others fall naturally into distinct groups'^ 

 the members of which resemble one another very closely but differ from 

 all the other groups in certain important particulars. This rather suggests 

 that the groups are made up of forms which have been sej)aratcd into 

 species on the basis of characters which are not of sufficient importance or 

 stability in themselves to rank as specific characters, and that they are, at 

 most, only variations of one species. 



A typical group of this kind is that which includes the species C. Lemn'je, 

 Cohn, C. Knyanum, Cohii & Szymansld, C. pallidum, Kiebs, and C. ArcherC 

 anum, Hieron. ; and it is significant that the last two species have not a-ain 

 been recorded since their first description. 



* Whitting, F. E. " On CHorocystis Sarcophjci, a new endopliytic Alga." In G Murr-tv 

 Phyc. Mem., Part II. p. 43 (1893). • ' - j 



t Moore, G. T. « New or little known Unicellular Al-aj : I. Chlorocydis Cohnii." Bot 

 Gaz. vol. XXX. (1900) p. 100. 



X Gardner, N. L., in Univ. Calif. PuW. 13ot. vi. no. 14 (1917). 



_ §_ Cunninghani, D. D. " On an endophytic Alga occurring in the leaves of Zunnanthcnmm 



'^ TZWo.^. ■ ^^'^'""^ '^^'''' "^ ^*™^ ^f I^^i^' Ed. Sir Benj. Simpson, 



Part III. (1887) pp. 33-40. ^ ' 



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