72 THE LILAC MILDEW. 



e. The number of spores (ascos pores} in each; their shape; 



their arrangement. 

 /. Draw an ascus with its spores. 



6. Examine younger and younger ascocarps to as early a stage 

 as can be found. Draw. 



IV. THE SEX-ORGANS. 



The very simple sex-organs are not easily found ; * if seen, 

 observe: 



1. The larger axial cell, the carpogonium, homologous with 

 oogonium. 



2. The smaller lateral cell, applied closely to the carpogo- 

 nium, the antheridium. 



3. Draw. 



ANNOTATIONS. 



The group of plants to which Mkrosphara belongs, 

 a very large one, is characterized by having a special 

 covering for the spores, known as the ascus. This is 

 developed probably as a result of fertilization. Except 

 in some of the higher forms, fertilization takes place 

 much as in many other plants, but the subsequent devel- 

 opment is very different, for an outgrowth of the plant 

 from the portion immediately below the organs of fertili- 

 zation at once arises which eventually envelops the form- 

 ing spores and develops into the body of the ascocarp. 



It is quite possible that Microsphara has reached an 

 advanced parthenogenetic stage, i.e. the "fruits" may 



1 In most material it will not be possible to find these organs. To 

 get a good notion of them examine the cuts illustrating ascomycete re- 

 production in the text-books; also in a special article by R. A. Harper, 

 on sexual reproduction in Pyronema confluens, and the morphology 

 of the ascocarp; in Ann. of Bot. 14: 1900. (This paper contains a good 

 bibliography of the entire subject.) 



