96 STUDY OF COMMON PLANTS. 



ORGANS OP FLOVTERLESS PLANTS. 

 I. Spores. 



1. Non-sexual spores. These are to be obtained in. the 



greatest number and variety. Such are the coni- 

 dia of the Peronosporese, the uredo and teleuto- 

 spores of the Uredineee, the resting spores of the 

 Ustilaginese, the zoospores of Myxomycetes, Pero- 

 nosporese and various algse, the spores of mosses, 

 , and many others. They agree in the essential 



feature that they are produced simply as vegeta- 

 tive cells, without the intervention, so far as is 

 now known, of any sexual process. 



2. Sexual spores. Zygospores of Spirogyra and of the 



Mucorini, representing the simplest form of sexual 

 reproduction; oospores of Peronosporese, Sapro- 

 legniaceae, Vaucheria and other algse, representing, 

 with the corresponding male bodies, the simpler 

 cases of differentiation of the sexes ; the reproduc- 

 tive cells of the archegonia and antheridia of 

 mosses and liverworts, showing a still farther dif- 

 ferentiation ; and lastly the corresponding bodies — 

 oosphere and antherozoids — of vascular crypto- 

 gams, the series leading up finally to homologous 

 reproductive elements in the flowering plants. 



II. Germination. This is readily studied by observing 

 and providing the conditions of germination as they exist 

 in nature, though artificial media are often serviceable, and 

 in case of protracted study of many forms are indispen- 

 sable. The study should include 



1. Observation of changes that take place in the spore 

 itself. 



