202 MISCELLANEOUS EXAMPLES 



chytrium are characterised, as I have said, by a greatly distended and 

 almost circular stoma, and often by having their walls stained of a 

 more or less distinct rust colour. Indications of the latter change 

 can be seen in Fig. 26, C, D.' It is a fact of much importance 

 that Diatoms are never to be found in any of the sub-stomatal 

 spaces except in those which either actually contain, or bear marks 

 of having been previously tenanted by, Chlorochytrium. 



There is another point of much interest to be mentioned. 



Sometimes one of the epidermal cells, of zig-zag outline, will 

 here and there be found filled by a light green Alga, having the 

 appearance of being a species of Chlorochytrium, as in Fig. 29, A 

 ( ^ 375)- Other of these cells may be found in which such bodies 

 seem about to undergo fission into several smaller cells, as in B ; and 

 others still in which the original cell has divided into small green 

 ovoid products (C), or into a number of more minute zoospores. In 

 one case such zoospores were seen to have assumed a yellow colour, 

 and some of them seemed to be elongating, as was the case with 

 some of the segments shown in D. Many other of these isolated 

 epidermal cells have been found containing either small ovoid 

 Diatoms only (Fig. 29, F), or a mixture of such Diatoms with green 

 fission products, as in E ; just as I have found the two kinds of 

 bodies associated in the much larger sub-stomatal spaces. 



The Diatoms in the epidermal cells are always small, commonly 

 of about the same size, but not invariably so, and mostly have the 

 appearance of being minute Naviculas. 



How the Chlorochytrium spores obtain an entry into these 

 epidermal cells I am unable to state ; but being actively motile it 

 would clearly be much easier for them to get in, than for the 

 Diatoms to do so. 



It seems most probable that it is the spores of Ch. Knyanum 

 which infect these epidermal cells, and that they may penetrate 

 them from a sub-stomatal space, since I have often, though by no 

 means invariably, found such infected epidermal cells just over, or 

 by the side of, one of these spaces. 



What interpretation is to he given concerning the Association of the 

 Diatoms with the Chlorochytrium fission products ? 



Only two possibilities seem to present themselves : — 



• Of course these two characteristics, belonging to different planes, can never 

 be seen together in the same photograph. 



