306 PT7CCINIA. 



440. Infection of the Barberry. The sporidia produced 

 by the germination of the teleutospore do not germinate on the 

 Wheat, but infect the leaves of Barberry. 



(a) Cut twigs of Barberry in spring, when the buds are unfolding ; 

 remove some young leaves, place them on wet blotting-paper, put 

 a drop of water on each leaf and add a few teleutospores (from 

 a batch which have shown signs of germination, if possible) ; 

 after a full day, cut tangential sections from a leaf, so as to obtain 

 the epidermis, where the teleutospores were sown, and look for the 

 sporidia, which may be seen putting out a hypha. This hypha is 

 able to eat its way into the leaf (by secreting cytase and other 

 enzymes), and therefore does not need to make use of a stoma in 

 order to infect the leaf. 



(b) Also try infecting in this way some young leaves on a . 

 Barberry twig placed in Knop's solution in a large jar. 



(c) In these plants, or in Barberry bushes growing under natural 

 conditions, note that the leaves often show in spring swollen 

 discoloured patches due to the growth of the mycelium produced by 

 the entrance of the hypha (germ-tube) emitted by the germinating 

 sporidium. 



441. Aecidia on Barberry. Examine a Barberry 

 leaf showing these blotches. At some points on the 

 underside of the leaf the cup-like aecidia may be seen 

 with naked eye or lens, while at other places the" yellowish 

 blotches will be seen as swellings young aecidia which 

 have not yet burst through the epidermis of the leaf. An 

 open aecidium has the form of a cup with a ragged and 

 outwardly curved margin; its yellow contents are the 

 aecidiospores. On the upper side of the leaf look for 

 much smaller projections, appearing as minute pointed 

 warts these are the spermogonia, better seen in section. 



442. T. S. of Barberry Leaf, with Aecidia and 

 Spermogonia (Fig. 65). Cut transverse sections of 

 Barberry leaf showing groups of aecidia ; mount in 

 glycerine, and note (1) the mycelium of the Puccinia, 

 the hyphae of which ramify through the intercellular 

 spaces and, especially in the spongy lower mesophyll, are 

 so closely packed that the mesophyll cells may be widely 

 separated from each other and appear embedded in a 

 dense matrix of mycelium ; (2) an aecidium, cut through 

 the middle and therefore appearing U-shaped, containing 



