66 PROTECTION OF PLANTS — 1924-25 



rile water did not germinate to any extent. These examined a week later were 

 found to contain a number of the larger thicker-walled spore which had become 

 septate. The spores germinate first by one germ tube which is generally 

 followed by a second from the opposite pole. This is sometimes followed by a 

 third from the side. Germination may be slow and the developing germ tube 

 may look like a secondary spore for a while. The germ tube becomes septate 

 very early and also soon branches. 



The spores are borne in pycnidia that vary greatly in size, 75 to 100 mi- 

 crons being the size of the smaller. The pycnidia on potato dextrose and all 

 other n:edia that is especially favorable for growth appear as if multi-ostiolate 

 but it is considered that this is due to a coalescing of the pycnidia which are very 

 numerous during their formation as sections cut through a developing colony 

 show that this is quite possible. On colonies that are on a rather unfavorable 

 sul stratum the pycnidia are far apart and there is generalh^ only one ostiolum. 

 The larger of the pycnidia measured 175 microns in diameter. The pycnidia 

 are very delicate as the walls are only made up of two to four layers of thick 

 walled, slightly darker cells that form a pseudo-parenchymatous tissue. Old 

 pycnidia may become nearly black but the immature ones are as a rule trans- 

 lucent. This seems to depend on the substratum for on some media they are 

 very difficult to see; the pink mass of spores n the centre with the dark ring 

 of cells around the ostiolum being all that could be easily seen. In all but the 

 very Hack pycnidia the ostiolum showed as a ring, but on sectioning pycnidia 

 it was seen that it really is a short neck made up of cells similar to those in the 

 walls and 5 to 6 microns long. As the spores mature in the pycnidia they are 

 forced out in a pink mass. In cases where the pycnidia are on the surface of 

 the substratum they ooze over the surface and give the colony the same appear- 

 ance as that of a heavily sporulating colony of C. lindemuthianum. Where the 

 pycnidia are embedded in the substratum the spores are forced out in any direc- 

 tion and the result is that a colony that is some three weeks old has little pinkish 

 masses of spores forced down into the medium from the bottom of the colony. 



The mycelium is variable in diameter, some being 11 microns wide with 

 cells 15 to 30 microns long. Such mycelium branches and rebranches until it is 

 of a fine distributive nature at the edge of the colony. The cell contents are 

 hyaline and contain large oil droplets or vacubles which are more prominent as 

 the colony ages. The pycnidia are placed in the norma' colony in an indefinite 

 manner There is no sign of a stroma only a few strands of dark mj^elium 

 growing around each pycnidium. In a colony that grew on a very unfavorable 

 medium, and in another on potato dextrose agar at 140 C, the pycnidia were 

 formed in branched radiating rows towards the edge of the colony as though 

 following some special strand of mycelum. A few hanging drops of agar were 

 left after one of the gernjination tests and on being examined later it was noticed 

 that three small pycnidia had developed. 



Appearance in pure culture. 



The colony starts as a few radiating stands of white mycelium and shows 

 clearly in from two to three days after the plate has been poured. The colonies 



