REPORT OF THE BOTANIST. 177 



visible intlio crevices of the bark. These greenish patches gradually increase until in 

 some instances they completely cover the whole surface of the excrescence with a soft 

 velvet-like coat. Such specimens were once sent to me from the West, where they hail 

 been pronounced by a scientific journal to bo a new species of black-knot. A micro- 

 scopic examination of this greenish coating reveals the fact that it is composed of in- 

 numerable upright jointed flexuous threads or flocci which bear upon their summit 

 oval or oblong spore-like bodies, at first simple, but soon becoming one or more septate. 

 This is the first external development of the fungus, and in the systematic classification 

 adopted by botanists it belongs to the genus Cladosporium. This genus, however, we 

 apprehend is destined to be overthrown, its species being only an early form of devel- 

 opment of species of Sphajria. Indeed those celebrated European mycologists, Tulasno 

 and Cooke, already deem the very common Cladosporium herbarum to be only a condi- 

 tion of Sphwria lierharum. And here we have another quite clear case of a sijuilar 

 dimorphism, for I have never yet seen a young black-knot excrescence of the 

 cherry-tree in spring on which I could not detect the Cladosporium. In a few weeks 

 this Cladosporium growth is succeeded by numerous minute black globular bodies 

 scarcely as large as the head of a small pin. These usually cover the whole surface of 

 the excrescence, and are often so closely crowded together that they partially lose their 

 globose form. This stage of the fungus development, has evidently been mistaken by 

 some for its complete development. In the work of Harris, on Injurious Insects, we find the 

 following statement in reference to this fungus : " They come to their growth, discharge 

 their volatile seed, and die in the course of a single summer." And in the Practical 

 Entomologist for March, 1866, we find this statement : "Toward the middle of August, 

 the new black-knot, having perfected its seed, gradually dries up and becomes inter- 

 nally of a reddish-brown color. In other words, like so many other annual plants, it 

 dies shortly after it has perfected its seed." Again, in the March number for 1867, ISIr. 

 Walsh says, " I showed that black-knot is nothing but an assemblage of minute fun- 

 guses, which perfect their seed or ' spores,' as botanists term it, the latter end of July ; 

 and that consequently, as this fungus is an annual jilant, by cutting oft' and destroyiijg 

 the black-knot early in July its further propagation may bo efl'ectually stopped." 



Now, according to all of our observations, the seed of the fungus is not j)erfccted in 

 July and August, nor indeed until some months later. Externallj^ it is true, the fun- 

 gus appears to have attained its full development, but if ono of these little black 

 globes— peritliecia, they are called by botanists — be taken from the tree at this time 

 and crushed on the side of the microscope and its contents examined, little oblong 

 pale membranous sacks will be seen. They are ]iot 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 bo formed. The earliest 

 period in which we have found the spores developed is the middle of January. In 

 specimens collected January 13, 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 four- 

 teen months from the time of its first external 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 determining the propertime for cutting 

 off the excrescences. Some report that they have tried this remedy without success. 

 Want of success may be ascribed to three causes : 



1st. The remedy may not be employed at the proper time. If the black-knots be 

 trimmed off in summer or even in spring, it is evident that the trouble will not be 

 effectually cured, for the whole or part of a crop of spores will already have been dis- 

 seminated to produce new excrescences the following antumn and spring. It is true 

 if the cutting i:)rocess be carefully repeated at sufliciently short intervals, it would in 

 the end accomplish the desired result if done at any time, provided the tree could 

 endure the frequent repetition of the operation. But, in our opinion, November is the 

 best time for cutting off and destroying the knots. At this time the coming crop of 

 spores is not mature, the leaves do not hinder the ready detection of the swellings, 

 and the young excrescences, the foundation of a second succeeding crop, are also theii 

 visible to a close observer, so that thorough work may be done at one operation. 



2d. The operation may not be properly performed. Physicians, in the excision of a 

 cancer from the human body, insist upon the necessity of an entire removal of every 

 particle and fiber of the extraneous growth. So in this case, wo must insist on the 

 complete removal of all the affected part of the branch. It has already been stated 

 that in November new swellings appear just below the old excrescences. Should the 

 old excrescence be cut 'oft' just before the appearance of this new swelling, it is quite 

 13 A 



