334 DISEASES OF FIELD & GARDEN CROPS. [en. 



Museum at South Kensington. This slice exhibits 

 numerous unusually large sporangia of a fungus not to 

 be distinguished from Protomyces. Very little mycelium 

 can be detected ; and many of the sporangia of the fungus 

 are situated in positions where the tissues of the host 

 plant have apparently, but perhaps not really, decayed. 

 We have illustrated one sporangium of this fungus, which 

 may be named Protomycites protogenes, W.Sm., at Fig. 

 140, enlarged 400 diameters (protogenes, first produced or 

 primaeval). In most of the silicified examples an outer 

 or exospore, and inner or endospore are distinctly visible. 

 This fungus presents some analogy with the alga 

 named Chlorochytrium Lemnce, Cohn., which grows within 

 the fronds of duckweed, the spores from the zoosporangium 



FIG. 141. 

 Diagram showing development of simple fungi by cell-division. 



of which conjugate or fuse in the style of the zoospores 

 (or zygozoospores) of Protomyces, and so produce zygospores. 

 The observer should, however, be ready to distinguish, 

 between mere fusing, which is very common in fungi, 

 and true conjugation, which is by no means common. 



Although these two fungi have been detected in 

 Palseozoic rocks, it must not be concluded that they 

 are the simplest known forms of primal fungi. In 

 Peronospora and Protomyces alike, sexual organs occur; 

 and the fact of a separation of sexes shows a great ad- 

 vance upon a primordial form. Besides, the members 

 belonging to the two genera are parasites, and doubtlessly 

 lived in Palaeozoic times, as their representatives do now, 

 upon the living tissues of more highly-organised plants. 



