SECRETARY'S PORTFOLIO. 525- 



as follows: The Black Knot (Sphceria morbosa), so injurious to the plum 

 and cherry trees, forms an illustration of another family of fungi, many 

 members of which are considered perennial. The fungus attacks the young 

 branches, causing them to swell several times their natural size. The 

 enlarged portion of the branch is made up of a vast number of minute 

 threads, which increase in length and size until the bark of the twig is rup- 

 tured in one or more places. An olive-green covering soon forms over the 

 exposed part, consisting of spores borne singly upon the tips of fungus 

 threads. These simple reproductive bodies quickly pass away and spread the 

 disease to other parts. Later in the season the knot becomes incrusted and 

 a second form of spore is produced, very different in form from the simple 

 oval ones already mentioned. As autumn approaches the knot assumes a 

 black and rough appearance. In the hard crust small pits are formed, in 

 which spores are slowly produced within long slender sacs. These spores 

 are not ripe until towards spring. In this well-named black knot we have a 

 fungus with at least three forms of spores, one of which serves the important 

 purpose of carrying the species through the winter season in a form admit- 

 ting of a ready dispersion in the early spring. The knots last for more than 

 one season, thus showing that the whole community of fungus life on a 

 single cherry branch is perennial. This is well shown when a gardener fails 

 to cut away the branch for a sufficient distance below the affected part, in 

 which case the remaining end will develop into a well-formed knot the 

 following season. The filaments of the fungus extend for a foot or more 

 below the swelling, and live on from year to year. 



With regard to the destruction of the fungus which causes the above 

 disease the Eural Canadian observes : Watch your trees carefully, and when- 

 ever the black tumor appears cut it off and destroy it. Should it appear 

 on the trunk or large limbs of a tree, cut away the diseased part carefully, 

 and apply a wash of chloride of lime or a coating of spirits of turpentine. 

 It is well also to give the soil around the tree a liberal application of wood 

 ashes and so strengthen its constitution to resist the attacks of the disease. 



Potato Scab. — The Prairie Farmer interviewed Prof. Burrill with reference 

 to the quite prevalent malady " potato scab," bringing out the following state- 

 ment: 



That the cause of the injury called "scab" upon the potato has not been 

 well worked out, and it cannot be asserted as certainly known. Probably sev- 

 eral diseases are included under this common name. But a negative point 

 which may be considered thoroughly settled, is, that insects are not the authors 

 of the mischief. There is, to be sure, an appearance of insect work, but 

 nothing whatever has been observed to prove that they have anything to do 

 with the malady, while many facts disprove it. 



The diseases has been attributed to earth-worms, but in this again we have 

 only guess work, and the negative evidence is quite strong. One or more 

 species of fungi have been accredited with the destructive work, yet little is 

 really known about these as agents, rather than results. A fungus named 

 Rhizoctonia solani is found on potatoes, leaving, either singly or in groups, 

 little pustules in the skin, making a peculiar roughness, which is called scab- 

 by many. This, however, is certainly different from the corroded spots to- 

 which the name is more appropriately applied. 



