GENERAL CHAEACTERS OF PROTOPHYTES. 



251 



actions, between their component cells; each one of these being 

 a repetition of the rest, and no relation of mutual dependence 

 existing among them. All such organisms may well be included 

 under the general tei-m of Protophtftes, by which it is convenient 

 to designate the primitive or elementary forms of Vegetation ; 

 and we shall now enter, in such detail as the nature of the pre- 

 sent Treatise allows, into the history of those forms of the group, 

 which present rpost of interest to the Mieroscopist, or which best 

 serve to illustrate the general doctrines of Physiology, 



150. The life-history of one of these Unicellular Plants, in 

 its most simple form, can scarcely be better exemplified than in 

 the Palmoglcea macrococca (Kiitzing) ; one of those humble kinds 

 of vegetation which spreads itself as a green slime over damp 

 stones, walls, &c. 



When this slime is Fig- 67. 



examined with the 

 microscope, it is 

 found to consist of a 

 multitude of green 

 cells (Fig. 67, a), each 

 surrounded by a ge- 

 latinous envelope ; 

 the cell, which does 

 not seem to have any 

 distinct membranous 

 wall, is filled with 

 granular particles of 

 a green color ; and a 

 "nucleus" may some- 

 times be distinguish- 

 ed through the midst 

 of these. When treat- 

 ed with tincture of 

 iodine, however, the 

 green contents of the cell are turned to a brownish hue, and a 

 dark-brown nucleus is distinctly shown (g). Other cells are seen 

 (b), which are considerably elongated, some of them beginning 

 to present a sort of hour-glass contraction across the middle ; in 

 these is commencing that curious multiplication iy duplicative 

 subdivision, which is the mode in which increase nearly always 

 takes place throughout the Vegetable kingdom ; 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 proceeded to the extent of com- 

 pletely cutting oft' 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 



Various phases of development of Palmoglfsa macrococci; 

 A, full-grown cell ; B, c, d, e, successive stages of binary 

 subdivision; ■ F, row of cells, produced by succession ol 

 subdivisions ; g, h, i, cells treated by iodine ; K, L, M, cells 

 in conjunction. 



