IN THE VEGETABLE KINGDOM. 21 



in the mode of perforation of the cell-wall, and the invest- 

 ment of the embryonic corpuscule. 



In the higher Cryptogamia another modification of the 

 reproductive process prevails, in which the sexual elements 

 are represented by phytozoa and archegonial corpuscules. 

 LinngBus was led to apply to the class in which he placed 

 these species, the name of Cryptogamia, from his not being 

 able to extend to it those principles of sexual relation which 

 he recognised in the higher plants. But since his time, 

 after much groping on wrong tracks, relations of this na- 

 ture have at last been detected, more closely analogous in 

 some respects to the reproductive phenomena of animals, 

 than even those with which we were previously acquainted 

 in phanerogamic plants. The analogy lies mainly between 

 the spermatic or fertilizing elements in the two kingdoms, 

 the vegetable phytozoa, being like the spermatozoa of ani- 

 mals, minute rounded or filiform bodies, endowed in general 

 with motile powers by the action of ciliary appendages. 

 The germinal element, which is lodged in the centre of a 

 flask-shaped group of cells, termed the archegonium, appears 

 to be at first a homogeneous mass of protoplasm, but after 

 fertilization by the phytozoa, it becomes a true cell by the 

 development of a distinct wall on its exterior. There is a 

 great similarity throughout the gToup, in the general cha- 

 racter of both kinds of corpuscules, and in their immediate 

 investments, but very great diversity in their relations to 

 the parent stock. Sometimes, as in mosses, they are de- 

 veloped at once on the leafy axis ; in other cases, as in ferns, 

 they are formed in detached phytoids, resembling distinct 

 plants of a lower type — peculiarities which will come again 

 to be noticed, in reference to the contrast between these 

 two families, as representing opposite forms of alternation 

 of generations. 



The remaining modification of the reproductive process 

 ^— that by pollen grains and ovules — characterises all the 



