IMPROVEMENT IN THE ARRANGEMENT OF FERNS. do3 



the germ cell. This latter, thus acted upon, comiuenced growth^, 

 assuming the true fern form, its fronds producing in the proper place, 

 accordiog to their kinds, innumerable sporangia, bearing spores by 

 which the same succession of phenomena would be repeated. It seems 

 to follow that the cellular disk, small and unimportant as it appears, is 

 the perfect plant in its most active condition, and that what we know 

 as the ferns constitute a secondary growth, specially devoted to extend- 

 ing the reproductive power by its production of spores; one fertilized 

 archcgonium, instead of itself becoming a spore, putting forth a plant 

 producing spores not only in vast numbers but through successive years. 

 Here we see fully displayed the difference, already referred to, between 

 Anogens (Charals, Hepaticals and Muscals) and Acrogens (Equisetals, 

 Lycopadials and Filicals). In the former the staminodia and archegonia 

 are produced, together or separately, at certain points on the growing 

 plant, and the fertilized archcgonium developes a sporangium bearing 

 numerous spores, the prothallus being transient, and the process in 

 perennial species, being renewed from year to year: in the latter the 

 stamioodia and archegonia occur only in the tissue first developed from 

 the growing spore, called the prothallus; and the product of fertilization 

 is not a sporangium, but a plant bearing numerous sporangia with their 

 spores as long as the plant subsists. It seems plain enough that this 

 distinction is of such importance as to be properly regarded as the sign 

 of a class; and thus, giving that rank to Thallogens also, we have three 

 classes of the ilowerless plants, Cryptogamia of Linnceus, Acotjledoncs 

 of Jussieu. The classes named, though well distinguished each from 

 the others, and all of them of great extent, offering important variations 

 within themselves, are so strongly bound together as spore-bearing 

 plants, and as being destitute of vascular tissue, except in the case of 

 the secondary growth in Acrogena3, where that tissue is of a special 

 kind, differing in its nature and arrangement from that of higher phuits, 

 that any system not plainly recognising this connection of the three 

 classes, as well as their differences, must be pronounced unnatural. 

 Jussieu's three great divisions — Acotyledonese, Monocotyledonea? and 

 Dicotyledone^ — though, of course, as any knowledge of nature would 

 lead us to anticipate, there are transition forms near the boundaries, are 

 real natural divisions, confirmed by a variety of important characters ; 

 and his names, both in right of priority and as being derived from the 

 principal character, ought to be preserved ; but these divisions cannot be 

 compared with classes in the Animal kingdom. They represent the sub- 



