108 PRACTICAL BOTANY. 



B. jEcidium Stage. 



IV. Note in early summer on the leaves of Berberis 

 irregular bright yellow blotches, the tissues of the leaf 

 appearing swollen at those spots, and projecting con- 

 vexly on the lower surface, while the upper surface of 

 the blotch is usually concave : on the lower surface 

 numerous irregularly distributed yellow cups (aecidium 

 cups) may be seen projecting slightly beyond the 

 surface, while on the upper surface also may be 

 seen projecting organs of smaller size, and irregular 

 distribution (spermogonia). 



V. Cut transverse sections of a diseased leaf, so as to 

 pass through one of these blotches : mount some in 

 glycerine, others in Schulze's solution, and examine 

 under a low power : observe 



1. In the thinner normal part of the section, that 

 between the upper and lower epidermal layers there is 

 a mesophyll consisting of a single palisade layer, and 

 five or six irregular layers of spongy parenchyma. 



2. That the greater bulk of the infected part is due 

 not so much to increased number of the cells as to the 

 larger size of the individual cells and of the inter- 

 cellular spaces. 



In the sections prepared with Schulze's solution, if a 

 good staining has been effected, note with a low power 

 that the fungal tissues are but slightly stained yellow, 

 while the tissues of the host are stained in the usual 

 way, chiefly a dark blue. Recognise as the most 

 prominent parts of the parasite 



1. The aecidia, cup-like structures, containing a 



