604 LECTURE XXII. 



the only real and constant distinction between Phanerogams 

 and Cryptogams. 



In plants of comparatively low organisation the organs 

 which give rise to the asexually produced spores are usually 

 not confined to a particular part of the plant, though an 

 instance of this is afforded by \\\z pycnidia of the Pyrenomy- 

 cetous Ascomycetes, which are receptacles in which the 

 stylospores are produced. In the Muscinese the production 

 of spores only takes place in the capsule, which always con- 

 stitutes a considerable portion, and in some cases (Riccia) 

 the whole, of the body of the individual. In the vascular 

 plants (Pteridophyta, Phanerogams) the sporangia are, speak- 

 ing generally, confined to the leaves. In many of the Pteri- 

 dophyta the sporangiferous leaves do not differ in appearance 

 from the foliage-leaves; but in others they differ more or 

 less widely from them, as in the Equisetaceae, Marsiliaceae, 

 some species of Lycopodium and Selaginella, and notably in 

 Phanerogams. When the sporangiferous leaves differ widely 

 from the foliage-leaves in size, form, or colour, they are 

 usually aggregated together in groups on a branch, and such 

 an aggregate of sporangiferous leaves constitutes what is 

 known as a flower. In the Phanerogams the modification 

 of the sporangiferous leaves is so great that they have re- 

 ceived special names; those which bear the macrosporangia 

 (ovules) are termed carpels, and those which bear the micro- 

 sporangia (pollen-sacs) are termed stamens. 



We pass now to the consideration of the sexual pro- 

 duction of spores. This mode of spore-formation is known to 

 take place in nearly all families of plants above the Proto- 

 phyta; and in those in which, in spite of careful observation, it 

 cannot be detected, its absence is to be ascribed, not, as 

 in the case of the Protophyta, to the non-development of 

 sexuality, but to sexual degeneration. 



The following are plants or families of -plants in which no sexual 

 spore-formation has yet been discovered : 



Alga;: Cyanophyceae (Phycochromacese) ; Protococcaceae ; Spha- 

 celariae ; Laminariea?. 



Fnngii Schizomycetes ; Saccharomycetes ; Myxornycetes ; some 



