REPRODUCTION. 633 



spring, and the asexual reproduction goes on through the 

 summer, the sexual plant making its appearance towards 

 autumn. In Coleochsete it is only in the case of the sexually 

 produced spore that the nature of the resulting individual can 

 be predicted; it always gives rise to an asexual individual; 

 whereas the asexually produced spores gives rise to an 

 individual which may be either sexual or asexual, that is, to a 

 potential oophore. The life-history of Coleochaete is, then, 

 briefly this: the oospore gives rise to the sporophore; from 

 the zoospore of the sporophore a potential oophore is de- 

 veloped ; a succession of potential oophores then follows, 

 until finally, when the external conditions are appropriate, 

 an actual oophore is developed. In the Characeae the oospore 

 gives rise to a rudimentary individual, the proembryo, which 

 represents the sporophore. However, it does not produce 

 spores, but gives rise to the oophore (Chara-plant) vege- 

 tatively by budding. 



The study of the life-history of the Fungi is attended 

 with considerable difficulty, partly on account of the fact that 

 in many cases the development of the sexual organs is 

 dependent upon a combination of external conditions which 

 may but rarely present itself, and partly on account of the 

 great difference in habit which frequently exists between 

 the sexual and asexual forms of the same plant, a difference 

 which is sometimes accentuated, in parasitic Fungi, by the 

 occurrence of the two forms on different plants as hosts 

 (Heterceci&m). But in some cases the life-history has, never- 

 theless, been traced, and it frequently exhibits more or less 

 regular alternation of generations. Before entering upon the 

 consideration of these cases, it must be clearly understood 

 that the expression " sexually produced spore" will be applied 

 not only to those the formation of which is known to be 

 preceded by a sexual process, but also to those which though 

 formed probably or actually without an antecedent sexual 

 process, may be considered, as already explained, to be homo- 

 logous with those which are actually sexually produced; and 

 the individual producing such spores will be regarded as the 

 oophore. 



