OF THE DESMIDIEJE. 717 



former, indeed, is sometimes met with in various Desmidians, such as Cflos- 

 terium Lunula, &c., as well as other Algae. For a figure of this curious 

 parasitic growth attacking Eremosphcera viridis (de Bar j) (^= ChIoros2)hcera 

 OliveH, Henfi'ey, the former name having, we are inclined to think, the 

 priority), vide ' Micrographic Dictionarj^,' 2nd ed. pi. xlv. fig. 8. There can 

 be little or no doubt that some such parasite as that alluded to attacking 

 a species of Closterium has given rise to Ehrenberg's genus Polysolenia, 

 admitted indeed into the Desmidiaceae by Kiitzing, but which we here cannot 

 but exclude. 



The act of conjugation and formation of sporangia is not uncommonly to 

 be met with in several species. The after-development of the sporangium 

 seems to have been but very rarely Ts^tnessed; and the statement made in the 

 diagnosis is founded on the account given by M. Hofmeister (I. c), an extract 

 from which is given at page 17; also on the very similar account given by 

 M. de Bary, ' Untersuchungen liber die Famihe der Conjugaten : ' vide pi. 6, 

 shoAving the development of the sporangium of Cosmarimn Botrytis (III. 48- 

 54), and of C. MenegJiinii (III. 55-60), the nimiber of sister-cells formed 

 within the sporangium being fewer than in the instances cited by M. Hof- 

 meister. But although, in the cases cited by M. de Bary, the cells resulting 

 from the segmentation and individualization of the contents of the sporangium 

 are eventually of a Cosmarium-shape, it is, however, not until the young- 

 fronds commence self- division in the ordinaiy way, that the fii-st-formed 

 yoimg segments wholly assume the special characteristics of the species QII. 

 52, 53, 54 t 58, 59, 60). 



The nearest affinities of this family seem undoubtedly to be, on the one 

 hand with the Diatomacese (with which family, indeed, they were long 

 associated), and on the other with the Zygnemaceae (Conjugatse) ; while to 

 the Palmellaceae they also approach through the genus Penium, connected 

 with CyUndrocystis and Mesotaenium = Palmogloea {Kg.). 



It will be at once seen that the following arrangement of the species is for 

 the most part based on that laid down in Ralfs's ' British Desmidieae,' 1848, 

 in addition to which the following works have been consulted : — Kiitzing's 

 * Species Algaiiim,' 1849 ; Nageli's ' Einzelliger Algen/ 1849 ; Bailey's 

 (Smithsonian Contributions to Knowledge) ' Microscopical Observations made 

 in South Carolina, &c.', 1850 ; Brebisson's ' Liste des Desmidiees observees 

 en Basse Normandie,' 1856 ; de Bary {op. cit.), 1858 ; Papers in ^ Nat. Hist. 

 Review/ by Rev. R. Y. Dixon and by Mr. Archer, 1858-60. The first and 

 second of a series of papers by Dr. G. C. WaUich, F.L.S., descriptive of some 

 beautiful and interesting species of Desmidiaceae collected by him in Bengal, 

 had just made their appearance (' Annals Nat. Hist.' March and April, I860) 

 when we were obliged to go to press. It has seemed to us more advisable to 

 omit any description of those species than to introduce a few only without 

 having it in our power to do so with the whole. In indicating the sources 

 whence we have been able to derive information as to foreign species, it is 

 our pleasing duty to acknowledge the generous and courteous assistance of 

 M. de Brebisson in affording by letter the requisite information which that 

 distinguished and experienced observer has so largely at his disposal, and 

 without which our own acquaintance with the Continental forms not known 

 in this country would have been far more circumscribed. 



The following genera included in this family by Kiitzing in 'Species 

 Algarum ' are here excluded, as we conceive either that they are not truly 

 Desmidian, or the unnecessary splitting up of older genera : — 



Trochiscia, excluded ; Tetraedron, excluded ; Pithiscus = Cosmarium pyra- 

 midatum (Breb.) ; Stauroceras = Closterium, in part ; Polysolenia (E.) = a 



