164 DISEASES OF FIELD & GARDEN CROPS. [CH. 



with that of the dScidium cups. The mycelium gradually 

 approaches the upper epidermal cells by the intercellu- 

 lar spaces. When it is very near the surface it forms 

 minute knots similar with the knots of the AScidium 

 cups, but the growth differs in an important particular ; 

 for whereas the JEcidium cup grows from the base, as at 

 D, Fig. 84, the spermogonium grows by a constant pro- 

 trusion of new threads from the circumference to the 

 centre. A spermogonium, even when almost mature, is 

 like a brownish circular ball, with a loose enclosing mesh 

 of mycelial threads, and from this bark-like mesh innumer- 

 able rays of mycelium reach to the centre, the central spot 

 being darker than the rays. The name, spermogonium, 

 means a flask or case containing spermatia, and spermatia 

 are extremely minute bodies with a function supposed to 

 be similar with that of pollen. 



A ripe spermogonium is illustrated at Fig. 85, enlarged 

 300 diameters. It must be particularly noted here that this 

 spermogonium is magnified to twice the scale of its accom- 

 panying jEcidium cup, Fig. 84. This is necessary in 

 order to show the much finer details of all its parts. The 

 first thing to be noticed by the reader is that the constitu- 

 ent cells of the leaf, as at AA, although magnified twice 

 as many times as the similar cells at HH, Fig. 84, are 

 not nearly so large as the latter. The explanation of this 

 is, that the cells belonging to the upper part of the leaf 

 where the spermogonia grow are very much smaller in size 

 and much more closely compacted together than the cells 

 belonging to the lower and looser portion of the leaf. 



The upper epidermal cells of a barberry leaf are shown 

 at BC, Fig. 85, and burst apart at DE. The spermogonium 

 has no true wall or bark, but its entire outer surface is a 

 woven coating of extremely attenuated, brownish, some- 

 times almost granular mycelium ; this mycelium can be 

 traced into the adjoining intercellular spaces of the leaf, 

 as at FG. The illustration shows the mycelium belong- 

 ing to the outer surface of the immersed spermogonium 



