368 ON THE STUDY OF MICRO-FUNGI. 



the mycelium has developed to a certain extent, the areas in which 

 it is present will be distinguished by the green of the leaf being 

 changed into a reddish or purplish colour. Not only is the chlo- 

 rophyll affected, but, as might be expected from the presence of 

 such a growth in the tissues, the parts will very probably soon 

 become swollen and bulged out, giving a deformed appearance to 

 the leaf. 



When the mycelium is sufficiently far advanced, large numbers 

 of very fine hyphse or branches are given off from it. These 

 hyphse grow towards the epidermis, and their apices incline to a 

 central point, so as ultimately to form a flask-shaped body, termed 

 a spermogonium, immediately beneath the epidermis. The apex 

 of this body, spermogonium, then pierces the cuticle and becomes 

 visible on the surface of the leaf as a minute elevation. From 

 the ends of the hyphse, which project into the interior of the sper- 

 mogonium, are budded off a large quantity of very small, round 

 bodies, to which the name spermatia has been given. These 

 spermatia continue to increase in numbers till the whole cavity is 

 filled with them. 



The hyphse which form the apex of the spermogonium then 

 separate and make, as it were, a mouth to the flask, thus providing 

 a free passage from the interior of the body. Through this 

 passage the spermatia, which are held together by a sticky sub- 

 stance, gradually ooze out to the surface of the leaf, and it is 

 stated that this propulsion of the contents is due to the action of 

 moisture in causing the gelatinous matter which binds the sper- 

 matia to swell. Plate XVII., Fig. i, shows a section of a spermo- 

 gonium. When the spermatia are placed in water containing 

 sugar, it has been found that they multiply almost in the same 

 manner as the well-known yeast spores. Many experiments have 

 been made by those who make a special study of these objects 

 with a view of ascertaining definite information regarding their 

 functions, and of finding out what part they play in the life of the 

 fungus ; but it does not appear that any of the theories which 

 have been advanced can be considered as having given a satisfac- 

 tory explanation. 



The exit from the spermogonium is surrounded by the ends of 

 the hyphse, and they are supposed to act as a sort of hedge to 



