History of infusoria, including the desmidiaceae and diatomaceae, British and foreign / by Andrew Pritchard.

  • Andrew Pritchard
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: History of infusoria, including the desmidiaceae and diatomaceae, British and foreign / by Andrew Pritchard. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

    43/1074 (page 23)
    tion, and on the other to the PiilmelloDe, by the usually complete transverse division, and by the presence of a gelatinous investment. Indeed the relation to the latter is so intimate, that it is difficult to say to which family some genera belong. . . . Some species of Scenedesmus may be allowed to have an almost equal claim to raA with either. Agaia, they are related to the Diatomeas by similarity ia the reproductive process. In Ehi-enberg's system of Polygastria, the Closteria were placed together as a distinct family, imder the name of Closteiina, whilst all the other genera of Desmidiese were ranged as a section of the Bacillaria. This sepai'ation, based as it was upon presumed structural peculiarities, is no longer accepted by microscopists, who cojoin Olosterium with the several genera included in Ehrenberg's section Desmidiacea in one group—the DesmidieEe. The division of this family proposed by Mr. Ealfs is made according as— 1. The plant forms an elongated jointed filament (by incomplete division of its cells); or—2. The fi-ond is simple, from complete transverse division, and distinctly constricted at the junction of the segments, which are seldom longer than broad; sporangia spinous or tuberculated—rarely, if ever, smooth ; or— 3. The frond is simple, as above, generally much elongated, never spinous, frequently not constricted at the centime; sporangia smooth; or—4; Cells elongated, entire, fasciculated; or—5. The frond composed of few cells, de- finite in nimiber, and not forming a filament. This last section is so exceptional in general characters, and especially in the mode of reproduction, that Braun detaches it from the Desmidiese and associates it with the PalmeUeae. In this plan we coincide, and have there- fore treated separately this last section of Mr. Ealfs, comprehending Pedias- trum and Scenedesmus. Kutzing {Species Algarum) includes the Desmidiese in hia subclass Maia- COPHTCE^, suborder ChamEephycese. Mr. Ealfs enumerated 20 genera; viz.—In Sect. 1, Hyalotheca, Didymo- privm, Desmidium, Aptogonium, Sphcerozosma. Sect. 2, Micrasterias, Euas- trum, Cosmarium, Xanthidium, Arthrodesmus, Staurastrum, Didymocladon. Sect.^ 3, Tetmemorus, Penium, Docidium, Olosterium, Spirotcenia. Sect. 4, AnJcistrodesmus {Bhaphidium). Sect. 5, Pediastrum, Scenedesmus. When compiling his systematic work, Kiitzing appears not to have seen Mr. Ralfs's monograph, but only his detached papers in the Magazines, and consequently was unable to compare the genera estabhshed by the English author with those described by himself. The consequence is that Kiitzing describes several genera not admitted by Mr. Ealfs, who has otherwise dis- posed their representative species, disallowing the supposed distinctive generic character. Nevertheless it seems desu-able to enumerate the additional genera of Kiitzmg, since several are new (unnoticed by our English authority) and denved from the papers of Ehrenberg or of other obsei-vers, or from his own researches. Those instituted by Ehrenberg were introduced in oiu- last edition. ,Tr^x^V'^'^^°''^^f^f ^^■^^•■—Trochiscia (K.), Teiraedron (K.), PitMscus (K.), Stauroceros{K.) Polysolenia (E.), Microtlieca (E.), Polyedru n (Niigeh), thmm (K.), (Mcmmatonema (Agardh), Bamhusina (K.), Isthmosira (K.), fcZJi T (^^^^.^«^°?)', (E.), Oeminclla (Tmi^in), mnaciiJs trum{:^agch), Bhaphuhum (K.), Oocardium (Wdge]i). 'T^ S^''^™ instituted and their characteristics form «nLpnS^L^° systematic histoiy of the Desmidiea) by Mr. Ealfs in the subsequent portion of tiiis treatise.