172 



OTTO VERNON DARBISHIRE. 



The immediate product of germination seems to be a small heap of 

 perhaps 4 — 8 cells, one of which always comes to be near an ostiole 

 leading to an antheridial cavity. The antheridial cavities are de- 

 veloped in large numbers and very close together (Fig. 4, II.). A 

 filament is then formed, which passes into the host-plant through the 

 antheridial ostiole (Plate XVII., Fig. 1). 



Fig. 5. Phyllophora Brodiaei (Turn.) J. Ag. 1. 4-celled 

 antheridium with a spermatium at its apex. 2. Single 

 spermatium. 3. Antheridial cavity with ostiole at its 

 apex, x 1,000 cliam. 



It is worth while perhaps to draw attention to a former figure 

 which was intended to show the origin of the nemathecium of Phyll. 

 Brodiaei (2, Fig. 31). It shows the nemathecium arising from 

 the lower cells of the cortex or the outer cells of the medulla, 

 the filaments in question being drawn darker, to show them 

 up better. The drawing in itself is correct though misleading. It 

 only represents a portion of the initial filament of the nemathecium, 

 which in the other adjoining sections, had they been preserved, would 

 have been seen to originate from cells just outside one of the antheri- 

 dial cavities. Not unfrequently the spores seem later on to be drawn 

 down into the antheridial cavities, and thus no trace of their external 

 origin is left. 



After entering the host by the ostiole of the antheridial cavity, the 

 parasite immediately branches (Plate XVII. , Fig. 1), the branches at 

 first forcing their way into the internal medullary portion of the thallus of 

 the host. Very soon a differentiation takes place in the primitive thallus 



