558 MICROSCOPIC FOKMS OF VEGETABLE LIFE THALLOPHYTE8 



] (articles have little or no adhesion to each other ; or thev may pre- 

 sent themselves (2) in the condition of an indefinite slimy film, or (3) 

 in that of a tolerably firm and definitely bounded membranous 

 frond. The first of these states we have seen to be characteristic 

 of Palmoglona and Protococcus; the new cells which are originated 

 by the process of binary subdivision usually separating from each 

 other after a short time, and, even where they remain in cohesion, 

 not forming a ' frond ' or membranous expansion. The ' red snow/ 

 which sometimes colours extensive tracts in Arctic or Alpine regions. 

 penetrating even to the depth of several feet, and vegetating actively 

 at a temperature which reduces most plants to a state of torpor, is 

 generally considered to be a species of Protococcus ; but as its cells 

 are connected by a tolerably firm gelatinous investment, it would 

 rather seem to be a P<ili,i<<l1((.. The second is the condition of Pal- 

 metto, proper, of which one species, P. cruenta, usually known under 

 ' ' 



the name of 'gory dew 



s common on damp walls and in shady 

 places, sometimes extending itself over a 

 considerable area as a tough gelatinous 

 mass, of the colour and general appearance 

 of coagulated blood. A characteristic 

 illustration of it is also afforded by the 

 Hcematococciis sany.iimus (fig. 423), which 

 chiefly differs from Palmdla in the partial 

 persistence of the walls of the parent-cells. 

 so that the whole mass is subdivided by 

 partitions, which enclose a larger or smaller 

 number of cells originating in the sub- 

 division of their contents. Besides in- 

 creasing in the ordinary mode of binary 

 multiplication, the Palmetto, cells seem 

 occasionally to rupture and diffuse their 



PIG. 422. A, conjugating 

 microzob'spores of Ulo- 

 tlirix ; B, megazoiispore 

 of TJlot li rix, from Vines's 

 1 Physiology of Plants.' 



granular contents through the 



gelatinous 



stratum, and thus to give origin to a whole 

 cluster at once, as seen at <, after the 

 manner of other simple plants to be pre 

 sently described, save that these minute 

 segments of the endochrome. having no 



power of spontaneous motion, cannot be ranked as zoospores. 

 The gelatinous masses of the P<ilt<'U. are frequently found to con- 

 tain parasitic growths formed by the extension of other plant - 

 through their substance; but numerous branched filaments some 

 times present themselves, which, being traceable into absolute 

 continuity with the cells, must be considered as properly appertaining 

 tothem. Sometimes these filaments radiate in various directions from 

 a single central cell, and must at first he considered as mere exten 

 sions of this: their extremities dilate, however, into new cells ; and. 

 when theseare fully formed, the tubulax connections close up, and tin- 

 cells become detached from each other. 1 Of the third condition we 



1 This f a ,.t, fh'st ma <i,. ,, u i.lic hy Mr. Thwaites (Ami. of Xnt. Hint. 2nd series, 

 v I 1 ::l:; '- ls ""'' "f fundamental importance in the determination of the 

 real character <>!' this group. 



