Report on Botany. 



199 



knot is nothing but an assemblage of minute funguses, 

 which perfect their seed, or " spores " as botanists term it, 

 the latter end of July ; and that consequently, as this 

 fungus is an annual plant, by cutting off and destroying 

 the black knot early in July its further propagation may 

 be effectually stopped." 



Now according to all of our observations the seed of the 

 fungus is not perfected in July and August, nor indeed 

 until some months later. Externally, it is true, the fungus 

 appears to have attained its full development, but if one of 

 these little black globes — perithecia they are called by bo- 

 tanists — be taken from the tree at this time and crushed on 

 the slide of the microscope and its contents examined, little 

 oblong pale membranous sacks will be seen. They are 

 not all equally developed and are evidently rudimentary. 

 If we again examine the contents of some of the perithecia 

 collected at a later period, say in November, we shall find 

 that our rudimentary sacks have increased considerably in 

 size. They are now cylindrical and contain a greenish 

 grumous endochrome from which the spores are destined to 

 be formed. The earliest period in which we have found the 

 spores developed is the middle of January. In specimens 

 collected January 13th , spores were found in a few of the sacks 

 but most of them were yet filled with their greenish contents. 

 We have found spores in specimens collected as late as June, 

 therefore the time in which the fungus perfects its seed 

 may be said to be from January to June. Thus it will be 

 seen that the plant is not an annual, as some have affirmed, 

 but one that requires from fourteen to twenty months 

 from the time of its first manifestation as an incipient 

 excrescence to the time of the maturity of its seed ; and 

 from eight to fourteen months from the time of its first exter- 

 nal appearance as a plant to the perfection of its seed. If we 

 accept the knife as the sovereign remedy for this pest of 

 our fruit trees, these facts have an important bearing in 



