CRYPTOGAMS AND PHANEROGAMS. 235. 



differ from the barren ones, and are found associated with them, 

 and their formation does not limit the growth in length of the. 

 stem. It is only in a few of the true Ferns, and in the Hydro- 

 pteridege, that the fertile leaves differ considerably from the 

 barren ones. A division of labour in which certain leaves are set 

 apart for nutrition, and others for reproduction, is found more 

 pronouncedly in the Equisetincv and Lycopodince, for in these 

 groups, with a few exceptions, the fertile and barren leaves are 

 very dissimilar ; the former are collected in special ear-like cones, 

 which terminate the further growth of the short stems on which 

 they are borne. In connection with the cone, leaves are sometimes, 

 developed which form a transition from the barren to the fertile, 

 ones (the " annulus" in Equisetacece), and in these cases the first 

 indication of a flower with perianth or floral-leaves is to be traced. 

 Among the Cryptogams the highest division of labour is found 

 in Selaginella and Isoetes, which have the two kinds of sporangia 

 borne on different leaves. The division of labour (modification) 

 is, however, still more pronounced in the Phanerogams : the leaves 

 which bear the micros porangia (" pollen-sacs ") have quite differ- 

 ent forms from those which bear macrosporangia (the " nucellus " 

 in the ovule), the former" are termed stamens, the latter carpels; 

 in certain instances, too, there is even a contrast between the 

 " male plants" and the " female plants." Moreover, a division of 

 labour, in a much greater degree, takes place in the leaves which 

 do not directly take part in reproduction, and it is thus possible 

 in many plants to draw a sharp line not only between stamens and 

 carpels, but also between four or five distinct kinds of leaves, which 

 differ in form, structure, and corresponding functions, and which 

 appear in regular sequence on the shoot: namely, between " scale- 

 leaves " and " foliage-leaves," l both of which occur in the Crypto- 

 gams, and the " floral-leaves," including the bracts and leaves of the 

 "perianth," which latter often differ from each other in form and 

 colour, and are then separated into sepals and petals. The leaves . 

 stamens and carpels which bear the sporangia are termed sporo- 

 phylls, and the shoot, or extremity of a shoot, whose leaves are 

 modified into sporophylls, is terminated in its further growth by their, 

 production, and is known as a flower. The flower which is most 



1 Floral-leaves (hypsophyllary leaves) are here adopted as an equivalent of 

 the term " Hochblatter," to signify leaves on the floral-shoot other than foliage 

 or sporangia-bearing leaves. The term bract is applied only to leaves in whose 

 axil a flower is borne, and bracteoles to leaves borne on the flower-stalk (pedicel). 



