Report on Botany, 



197 



that the Cynips produced the excrescence, and later investi- 

 gators have failed to confirm his apparent suspicions. 

 Hence we do not think his mere association of the two 

 can have much weight either way. 



Like others from whose writings we have quoted, we 

 also claim to have examined the black knot carefully in 

 its various stages of development, not entomologically it is 

 true, but botanically, from which it is not unreasonable to 

 suppose that we may have observed some details in its 

 development which escaped their notice. "We desire, 

 therefore, to express the results of our own observations 

 and we desire this the more because in one or two points 

 we can not quite agree with the inferences and conclusions of 

 former investigators. 



If the smaller branches of a cherry tree that is suffering 

 from an attack of black knot be carefully examined in 

 November, some of them will be found to be slightly 

 swollen for a little distance immediately below the excres- 

 cences. The cuticle of the bark will be cracked open 

 here and there, revealing the soft tissues of the inner bark. 



If a minute portion of this inner bark be examined by 

 the aid of the microscope, slender jointed filaments or 

 threads may be seen, that have insinuated themselves among 

 the bark cells. These threads are the primary vegetating 

 condition of the fungus and are known to botanists as 

 mycelium. During the winter the enlargement of the 

 branch remains nearly or quite stationary, but with the 

 advent of spring and the renewal of vegetable activity, 

 the tumors increase in size, the chinks in the bark become 

 wider and more numerous, and by the end of May small 

 dark green stains are visible in the crevices of the bark. 

 These greenish patches gradually increase in size until in 

 some instances they completely cover the whole surface of 

 the excrescence with a soft velvet-like coat. Such speci- 

 mens were once sent to me from the west where they had 



