IN THE VEGETABLE KINGDOM. 55 



multiplication of the plant and we may farther compare 

 the sporangia of the former to the perichsetial involucre of 

 the latter, both being modifications of the prevailing type 

 of leaf-development. This is obvious in the moss, and it 

 is indicated also in ferns by the circinate development both 

 of fronds and sporangia, as well as by the occurrence of 

 certain transitional forms, like those through which the 

 ordinary leaves of Blechnum and Osmunda are depauperated 

 into the spikes of fructification, or like the leaf-shoots which 

 in some of the " viviparous" species take the place of the 

 sporangia themselves.* In Equisetum, too, we can trace in 

 the concentric arrangement both of the sporangia and their 

 peltate receptacles, a marked relation to the general type of 

 the whorls of primary and secondary branches, which repre- 

 sent the leaves a relation of the same general character as 

 that already noticed in the organs of Chara. 



8. LYCOPODIACE^E AND RHIZOCARPEJE. 



The Lycopodiacese of the present epoch are a group of 

 plants intermediate in habit between mosses and ferns. 

 They resemble the former in their prostrate and ramose 

 growth, and their minute scale-like leaves, while their 

 affinity to ferns is indicated by the nbro-vascular system 

 of the stem, and by the spores of the cauline fructifica- 

 tion not being the result of any prior act of impregna- 

 tion. In their process of reproduction they depart widely 

 from mosses, and occupy a position in some respects inter- 

 mediate between ferns and phanerogamic plants. But the 

 process has not been satisfactorily traced out, except in 

 tielaginella and Isoetes, which differ from the rest of the 

 order in having two kinds of spores, a lesser and greater, 

 termed respectively microspores and macrospores. The 



* Lindley Voget. Kingdom, p. 75. 



