lxxviii repokt — 1877. 



Thus in the whole tribe of the Ferns and Vascular Cryptogams, in the 

 higher Algas and Fungi, in the Characeae and in the Mosses, the differentia- 

 tion of the productive elements is carried to a very high degree ; for whilo 

 that belonging to the embryo or germ presents the structure of a simple cell 

 which remains at rest, or in a comparatively passive state, and, absorbing 

 into itself the substance of the other, becomes the seat of subsequent 

 development, the other, corresponding to the pollen of the staminiferous 

 phanerogam, is usually separated from the place of its formation, and, having 

 undergone a peculiar modification of structure by which it acquires active 

 moving cilia, it changes place and is directed towards the germinal structure, 

 and, coming in contact with its elementary cell, is more or less absorbed or 

 lost in the fertilizing process. The protoplasm of the germinal cell thus 

 acted on and fertilized then proceeds to undergo the changes of development 

 by which the foundation is laid for the new plant. 



In the Algte and Fungi, however, there are gradations of the differentiation 

 of the two reproductive elements which are of the greatest interest in lead- 

 ing to a comprehension of the general nature of the formative process. For 

 in the lower and simpler forms of these plants, such as the Desmidiea?, Heso- 

 carpese, and other Conjugatoe, we find that there is no distinction in structure 

 or form to be perceived between the two cells which unite in what is termed 

 conjugation ; and a complete fusion or intermixture of the two masses of 

 protoplasm residts in the production of a single, usually spherical, mass holding 

 the place of an embryo. And that there is an absence of specialization be- 

 tween the two uniting cells is clearly shown, in both Desmidium and Meso- 

 carpus, by the fact that the embryo or zygospore is formed in the mass 

 resulting from the union of the protruded portions of the two cells ; while 

 in more ordinary cases, as in Spirogyra, where the embryo is formed in 

 one of the two cells, it seems to be indifferent in which of them it is 

 formed. 



From this, which may be regarded as the most elementary type of new 

 production by the union of two cells, the transition is not a great one to 

 the development of a progeny without any such union. We might conjecture, 

 then, that the capacity for separate or individual existence extends in the 

 lowest organisms to the whole or to each structural element of their organi- 

 zation, while as we rise in the scale of vegetable life (and the same view 

 might apply to the animal kingdom) this capacity is more and more divided 

 between the two productive elements, or, at least, is only called into full 

 action by their combination. 



The germinal element of plants thus consists of a simple primordial cell, 

 varying in different kinds, but in all of them probably containing the essential 

 substance protoplasm ; and the most immediate result or effect of fertilization 

 is the multiplication by repeated fissiparous division of the previously existing 

 cells. The new individual resulting from this cellular growth usually remains 



