. The microscope and its revelations. tion of the stipe; so that the entire plantpresents us with a more or less complete flabella or fan upon thesummit of the branches, with imperfect flabella1 or single frustulesirregularlv scattered throughout the entire length of the beautiful plant is marine, and is attached to seaweeds andzoophytes. In the next family, that of Fragilariete, the frustules are of thesame breadth at each end, so that if they unite into a filament theyform a straight band. Insome genera they aresmooth, in others trans-versely striated, with acentral nodule ; w
. The microscope and its revelations. tion of the stipe; so that the entire plantpresents us with a more or less complete flabella or fan upon thesummit of the branches, with imperfect flabella1 or single frustulesirregularlv scattered throughout the entire length of the beautiful plant is marine, and is attached to seaweeds andzoophytes. In the next family, that of Fragilariete, the frustules are of thesame breadth at each end, so that if they unite into a filament theyform a straight band. Insome genera they aresmooth, in others trans-versely striated, with acentral nodule ; when stria1are present, they run acrossthe valves without interruption. To this familybelongs the genus gives its name to theentire group, that name(which means cuttingthrough) being suggestedby the curious habit of thegenus, in which the frus-tules, after division, sepa-rate from each other alongtheir lines of junction, butremain connected at theirangles, so as to form zigzagchains (fig. 451). Thevalves of Diatoma, when. FIG. 452. turned sideways (a), are Put. 451. FIG. 451.—Diatoma vulgare: a, side view of frustule; b, frustule undergoing division,seen, to be strongly marked FIG. 452.—Grammatophoraserpentina: a, front by transverse stria3, which tiustuie, o, o, front . IP • iincl euci views ot divided frustule ; c. frustule extend into the front View. about to undergo division; d, frustule com-The proportion between the pletely divided,length and the breadth of each valve is found to vary so considerably that, if the extreme formsonly were compared, there would seem adequate ground for regardingthem as belonging to different species. The genus inhabits freshwater, preferring gently running streams, in which it is sometimesvery abundant. The genus Fragilaria is nearly allied to Diatoma, thedifference between them consisting chiefly in the mode of adhesion ofthe frustules, which in Fragilaria form long, straight filaments withparallel sides; the filaments, ho
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
