THE LARCH CANKER 43 



spores from the ascus of this species is between 10 and 

 15 mm. In a damp chamber such as that described, the 

 spore-ejection may take place very rapidly, and from two 

 small apothecia, measuring 1-25 mm. and 1*5 mm. respec- 

 tively in diameter, 104 spores were found to have been 

 ejected in 2 minutes. In a dry atmosphere the asci cease to 

 shed their spores, a fact which -is no doubt correlated with 

 the closing of the apothecia in dry weather. 



The spores may germinate in either of the two following 

 ways : (i) The spores first divide by one, or less commonly 



FIG. 20. Spores and germination : A, spore, showing nucleus and 

 vacuoles ; B, germinating at both ends ; c, two germ tubes at one end ; 

 D, segmentation ; E, F, G, methods of germination. 



more septa which are put in at right angles to the long 

 axis of the spore (fig. 20, D, E). The first of these may be 

 completed twenty hours after the ejection of the spore. 

 When the spore becomes divided into three segments 

 (fig. 20, F) these are usually unequal, one being nearly half 

 the size of the whole spore ; a third septum may then be 

 formed in the larger cell. The germ tubes may arise in 

 many different ways. Most commonly one grows out from 

 each end of the spore, or one of them may originate near 

 the middle septum, but cases in which three or four germ 

 tubes arise from a single spore are not infrequent, (ii) The 

 spore may give rise to germ tubes without first becoming 



