MICROSCOPIC FORMS OF VEGETABLE LIFE. 



245 



243. With the two Protophytes just described may be ranked under 

 the general designation PalmellacecB a number of others scarcely less sim- 

 ple in their essential characters, but sometimes attaining considerable 

 dimensions. They all grow either on damp surfaces, or in fresh or salt 

 water; and they may either form (1) a mere powdery layer, of which the 

 component particles have little or no adhesion to each other, o* they 

 may present 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 

 Palmoglcea and Proctococcus; 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 

 colors 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 Palmella. The second is 

 the condition of the Pal- 

 mella proper; of which one 

 species, the P. cruenta, usu 

 ally known under the name 

 of ' gory dew,' is common on 

 damp walls and in shady 

 places, sometimes extending 

 itself over a considerable area 

 as a tough gelatinous mass, 

 of the color and general ap- 

 pearance of coagulated 



"hlnnrl A rliarnnl-PY'iaf ir> il Hcematococcus sanguineus in various stages of devel- 



3CL . A \ " opment: a, single cells, inclosed in their mucous envelope; 



lustration Of it IS also afford- b, c, cluster formed by subdivision of parent-cell; d, more 



T -i , -i TT i numerous cluster, its component cells in various stages of 



ea Dy tne rtCBmOtOCOCCUS division; e, large mass of young cells, formed by the sub- 



sanfiui n VU<* (Fip- 1 4-3 "I division of the parent endochrome, and inclosed within a 



V r i ' n -iVfl. " ^ '' common mucous envelope. 



which chiefly differs from 



Palmella in the partial persistence of the walls of the parent-cells, so that 

 the whole mass is subdivided by partitions, which inclose a larger or 

 smaller number of cells originating in the subdivision of their contents. 

 Besides increasing in the ordinary mode of binary multiplication, the 

 Palmella-cells seem occasionally to rupture and diffuse their granular 

 contents through the gelatinous stratum, and thus to give origin to a 

 whole cluster at once, as seen at e, after the manner of other simple 

 Plants to be presently described ( 245), save that these minute segments 

 of the endochrome, having no power of spontaneous motion, cannot be 

 ranked as zoospores.' The gelatinous masses of the Palmellae are fre- 

 quently found to contain parasitic growths formed by the extension of 

 other plants through their substance; but numerous branched filaments 

 sometimes present themselves, which, being traceable into absolute con- 



Stephanosphcera pluvialis; and is scarcely now to be considered an exceptional 

 phenomenon. 



