230 THE MICROSCOPE AND ITS REVELATIONS. 



the same manner that many Flowering-plants (such as the Potato), can 

 be propagated by the artificial separation of their leaf-buds. It fre- 

 quently happens among Cryptogamia, that this gonidial fructification is 

 by far the more conspicuous; the sexual fructification being often so ob- 

 scure that it cannot be detected at all without great difficulty. And we 

 shall presently see that there are some Protophytes in which the produc- 

 tion of gonidia seems to go on indefinitely, no form of sexual generation 

 having been detected in them ( 245). These general statements will 

 now be illustrated by sketches of the Life-history of some of those humble 

 Protophytes, which present the phenomena of cell-division, conjugation, 

 and gonidial multiplication, under their simplest and most instructive 

 a; pect. 



229. The first of these is the Palmoglma macrococca (Kiitzing) ; one 

 of those humble kinds of vegetation which spreads itself as a green slime 

 over damp stones, walls, etc. When this slime is examined with the 

 microscope, it is found to consist of a multitude of green cells (Plate 

 vni., fig. 1, A), each surrounded by a gelatinous envelope; the cell, 

 which does not seem to have any distinct membranous wall, is filled with 

 a granular 'endochromo' consisting of green particles diffused through 

 colorless protoplasm; and in the midst of this a nucleus may sometimes 

 be distinguished, but can always be brought irito view by tincture 

 of iodine, which turns the 'endochrome* cell to a brownish hue, and 

 makes the nucleus (G) dark brown. Other cells are seen (B), which are 

 considerably elongated, some of them beginning to present a sort of 

 hour-glass contraction across the middle; and when cells in this condition 

 are treated with tincture of iodine, the nucleus is seen to be undergoing 

 the like elongation and constriction (H). A more advanced state of the 

 process of subdivision is seen at c, in which the constriction has pro- 

 ceeded to the extent of completely cutting-off the two halves of the cell, 

 as well as of the nucleus (i), from each other, though they still remain in 

 mutual contact; but in a yet later stage they are found detached from 

 each other (D), though still included within the same gelatinous envelope. 

 Each new cell then begins to secrete its own gelatinous envelope, so that 

 by its intervention, the two aro usually soon separated from one another 

 (E). Sometimes, however, this is not the case; the process of subdivision 

 being quickly repeated before there is time for the production of the 

 gelatinous envelope, so that a series of cells (F) hanging-on one to another 

 is produced. There appears to be no definite limit to this kind of mul- 

 tiplication; and extensive areas maybe quickly covered, in circumstances 

 favorable to the growth of the plant, by the products of the binary sub- 

 division of one primordial cell. This, as already shown ( 226), is really 

 an act of growth, which continues indefinitely so long as moisture is 

 abundant, and the temperature low. But under the influence of heat 

 and dryness, the process of cell-multiplication gives place to that of ' con- 



the generative 'oospores.' If possessed of motile powers, they are spoken of as 

 'zoospores,' or sometimes (on account of the appearance they present when a 

 number are set free at once) as ' swarm-spores.' In contradistinction to ' motile ' 

 gonidia or ' zoospores,' those which show no movement are often termed resting 

 spores or statospores: but such may be either sexual oospores or non-sexual 

 gonidia; the latter, like the former, often 'encysting' themselves in a firm 

 envelope, and remaining dormant within it for long periods of time. Gonidial 

 spores, again, are sometimes distinctively named according to their size; some of 

 them, which consist of numerous cell-particles clustered together, being desig- 

 nated macro-gonidia, in contrast to the micro-gonidia consisting of single cell- 

 particles, which, when motile, are known as ' zoospores.' 



