QUESTIOX DRAWER. 



257 



If your correspondent refers to the super- 

 ficial roots of living- basswood and maple 

 which often run to some considerable dis- 

 tance, and hence disturb other plants, I may 

 say that I know nothing better than digging 

 and cutting them out. There is nothing- 

 that will prevent the roots g-rowing so long 

 as the trees are alive. It is part of the 

 nature of the root to send its branches where- 

 ever they can find nourishing matter — tood 

 and water. 



If the roots are already dead, then ag^ain 

 uprooting- is the best remedy. Some advo- 

 cate the use of coal oil or sulphuric acid. 

 These are undoubtedly potent, but the spade 

 and axe remedy is the simplest. 



O. A. C, Guelph. W. Lochhead. 



Rocky Mountain Cherry. 



1161. Sir, — Can you explain why I never get 

 fruit from my Rocky Mountain cherry tree ? 

 Anagance, N. B. C. Stockton. 



In answer to S. Stockton, Anag-ance, N. 

 B. , I would sug-g-est as the probable cause 

 of the flowers of his Rocky Mountain 

 cherry not setting fruit, that the flowers 

 are not perfect. If he procured some scions 

 from a Rocky Mountain cherry known to be 

 self fertile and g^rafted them on his trees, he 

 mig^ht be able to get some truit. 



C. E. F., Ottawa. W. T. Macoux. 



Exhausted Calcium Carbide as a Fertilizer. 



1 162. Sir, — Kindly give in your next Horticul- 

 turist some information as to the application and 

 value as a fertilizer of exhausted calcium car- 

 bide as taken from the generator of an acet}-- 

 lene gas machine ? 



Hagersville. S. W. Howard. 



The waste product from the acetylene gas 

 machine is practically slaked lime. If the 

 carbide has been manufactured from lime 

 free from metallic sulphides, as iron pyrites, 

 the by-product from the machine may be 

 adplied directly to the land. As, however, 

 it is apt to contain sulphur compounds 

 (which are injurious to vegetation), it is well 

 to expose it in small heaps on the field for a 



few weeks before mixing it with the soil. 

 This exposure corrects and renders harmless 

 the sulphur compounds. 



There are verj- few soils that are not 

 benefited by an occasional application ox 

 lime, say 20 to 40 bushels per acre eveiy 

 fourth or fifth year. For those that are 

 peaty, sour or naturally deficient in lime, 

 this waste product should especially prove a 

 valuable amendment. 



Frank T. Shutt, 

 Ottawa. Chemist Dom. Exp. Farms. 



A Disease of Wax Plants. 



Sir, — I send you herewith two leaves taken 

 from a Hoya Camosa. The plant is verj- large, 

 covering a frame about 4 ft. x 8 ft., and was, until 

 very lately, quite healthy looking. I would like 

 to know if it is possible to do anything to stop this 

 apparent blight or whatever it is. Have you ever 

 seen leaves of the Hoya affected in the same way? 

 Can you tell me what it is? I thought when I 

 first saw the spots that it had been some drops of 

 water on the leaves and scalded with the sun, but 

 I do not think this is the cause. I send two leaves, 

 on the large one you can see the blight in the first 

 stages, and on the smaller one the affected parts 

 have lost all substance. The plant is standing in 

 a square bay window with an east and south ex- 

 posure. As I feel anxious about the plant I would 

 like to hear from you at your earliest convenience. 



H. B. Sproat, Woodstock. 

 The disease affecting the wax-plant "(Hoya 

 carnosa) leaves is not a common one. It is 

 due to the presence of a fungus called Alter- 

 Jiaria, a genus allied to Cercospra and Mac- 

 rosporitim, which affect the tomato and other 

 plants. The mycelium of this fungxis lives 

 in the soft cells of the leaves, and spreads 

 with great rapidity. At first the spots are 

 but slightly aflfected, and resemble the re- 

 sults of sun-scald on drops of water sprink- 

 led on a leaf, but later the area of diseased 

 part widens, and the tissues begin to rot. 

 The margin of the area is very distinct. 

 Cultures of the fungus were made in the 

 laboratory here, and a fine crop of mycelium 

 and upright stalks, bearing conidia, was ob- 

 tained. Fig. 1835 shows ver)- clearly the 

 form of the threads and the conidia. The 

 latter are flask-shaped, and frequently united 



