466 PRACTICAL BOTANY 



closely packed mass of spores, and opening by rupture 

 through the lower epidermis of the host. 



2. The spermogonia, relatively small, flask-shaped 

 organs opening on the upper surface of the leaf. 



Having thus gained a general idea of the sections, 

 examine them in detail under a high power, and note 

 that in the infected patch the cells of the host are 

 apparently embedded in a felt of mycelium, consisting 

 of septate and branched hyphae, which traverse and 

 completely choke up the intercellular spaces : they are 

 but slightly stained with chlor-zinc-iodine, while the 

 cell- walls of the host plant assume a dark colour : they 

 are for the most part confined to the intercellular 

 spaces, and especially those round about the seciclia ; but 

 it is stated that occasionally they penetrate the cells of 

 the host, and though this is not easy to see, examples 

 of it should be looked for. Turning to the secidium 

 observe 



1. Its cup-like form. 



2. The dense felt of hyphse at the base of it. 



3. Immediately above this is the hymenium, a layer 

 composed of closely packed, parallel, rod-like cells 

 (basidia), arranged perpendicularly to the outer surface 

 of the leaf. 



4. The rows of spores, which have been successively 

 abstricted from the basidia: observe the hexagonal 

 form, thickened wall, and orange colour of the spores, 

 and the way in which the spores of contiguous rows 

 fit together. 



5. The peridium, consisting of a single layer of cells 

 enveloping the mass of spores : the form and arrange- 

 ment of the cells resemble that of the spores themselves 



