48 WHITE RUST. 



the oosphere, the fertilizing tube ; very difficult 

 to demonstrate. Draw. 



e. In older oogonia, more opaque roughened bodies 

 the oospores, formed from the oospheres. Note 

 i. The flexuous ridges on the exterior, 

 ii. The contents, in spores not too mature. 

 /. Draw some oogonia and accompanying antheridia 

 showing different stages of development of the 

 oosphere and oospore. 



Tease out some tissue containing oospores, which has 

 been boiled in potassic hydrate, stain lightly or not at all, 

 and notice 



g. The manner in which the oogonia and antheridia arise 



from the vegetative hyphae. Draw a few examples. 



//. The rather strong, pointed beak sometimes to be 



seen on one side the antheridium, the fertilizing tube 



which has been pulled out of an.oogonium. Draw. 



ANNOTATIONS. 



In Cystopus we have a much simplified condition of 

 an advanced type of development. The higher devel- 

 opment is shown in its sexual reproductive apparatus, 

 the sexual elements being quite dissimilar in size and 

 in behavior. The larger (female) element, the oogo- 

 nium, receives the protoplasm of the smaller (male) 

 element, the antheridium, the former remaining in a 

 passive state, while the antheridium is the active agent 

 in securing the union. This is the essential plan for 

 all higher plants, as well as for the group to which 

 Cystopus belongs, the Oophyta. 8 The transfer of the 



8 The terms Zygophyta, Oophyta and Carpophyta are used for the 

 three great groups of lower plants, in accordance with the suggestion of 

 Prof. C. E. Bessey in the American Naturalist, xvi (1882), p. 46, 

 and first introduced in his Essentials of Botany, 1884. 



