252 MICROSCOPIC FORMS OF VEGETABLE LIFE. 



envelope. Each new cell then begins to secrete its own gela- 

 tinous envelope ; so that, by its intervention, the two are usually 

 soon separated from one another (e). Sometimes, however, this 

 is not the case ; the process of subdivision being quickly re- 

 peated, 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 multiplication ; and extensive areas may be quickly covered, 

 in circumstances favorable to the growth of the plant, by the 

 products of the duplicative subdivision of one primordial cell. 

 This, however, is simply an act of G-roivth, precisely analogous 

 to that by which any one of the higher forms of Vegetation ex- 

 tends itself, and differing only in this, that the cells produced by 

 each act of cell-subdivision in the present case exactly resemble 

 that from which they sprang ; whilst in the case of more highly 

 organized Plants, they gradually become differentiated to a 

 greater or less degree, so that special " organs" are evolved, 

 which take upon themselves dissimilar yet mutually dependent 

 parts, in the economy of the entire organism. 



151. The process which represents the Gfeneration of the higher 

 Plants is here performed in a manner so simple, that it would 

 not be recognized as such, if we were not able to trace it up 

 through a succession of modes of gradually increasing complexity, 

 until we arrive at the elaborate operations which are concerned 

 in the production and fertilization of the seeds of Flowering 

 Plants. For it consists in nothing else than the reunion or 

 fusion together of any pair of cells (k), — a process which is termed 

 Conjugation; and it is characteristic of this humble plant, and 

 shows how imperfect must be the consistence of its cell-mem- 

 brane, that this seems to enter into the fusion, no less completely 

 than the cell-contents. The communication is at first usually 

 made by a narrow neck or bridge (k) ; but before long it extends 

 through a large part of the contiguous boundaries (l) ; and at 

 last the two cells are seen to be completely fused into one mass 

 (m) ; which is termed the spore. Each " spore" thus formed is 

 the "primordial cell" of a new generation, into which it evolves 

 itself by successive repetitions of the process of binary subdivi- 

 sion. It is curious to observe, that during the conjugating pro- 

 cess, a production of oil-particles takes place in the cells ; these 

 at first are small and distant, but gradually become larger and 

 approximate more closely to each other, and at last coalesce so 

 as to form oil-drops of various sizes, the green granular matter 

 disappearing; and the color of the conjugated body changes, 

 with the advance of this process, from green to a light yellowish- 

 brown. When the spore begins to vegetate, on the other hand, 

 producing a pair of new cells by binary subdivision, a converse 

 change takes place ; the oil-globules disappear, and green granu- 

 lar matter takes their place. Now this is precisely what occurs 

 in the formation of seed among the higher Plants ; for starchy 



