The Beneficial and Injurious Influences of Fungi. 197 



The Pine Disease (Peridermium pini) may be exterminated 

 by clearing away all plants of the Genus Senecio (Groundsels 

 and Ragworts) upon which it passes one of its life-stages. 



Anbury or Finger and Toe. (Plasmodiophora brassicce) 

 in Cruciferous plants (Turnips, Cabbage, etc.), can be prevented 

 by making the soil non-acid by limeing and by keeping in 

 check weeds of the same Natural Order in the field sides and 

 headlands. 



Fruit Scab and Canker ( Venturia incequalis) is averted 

 by spraying with Bordeaux mixture and by pruning off the 

 infected twigs. 



The Damping off of Seedlings (Pythium debaryanum) is 

 checked by ventilation and similar treatment as for Anbury. 



Smut and Bunt in Corn. ( Ustilago sp. and Tilletia 

 triteci) may be minimised by dressing the seed corn with 

 formaline or copper sulphate. 



Dryrot in Timber (Mertdius lacrymans) may be prevented 

 or eradicated by proper ventilation and by the application of 

 creosote solution. 



We read much about the breeding of plants which are 

 immune to certain diseases, but we have yet to learn of what 

 this so-called immunity consists. Is it because the stomata 

 are too small for the germinating hyph« of the spore to enter, 

 or is the virtue in the harder and less succulent epidermis of 

 the plants ? Dr. A. D. Selby has pointed out that in the 

 study of disease susceptibility it has been shown that other 

 features being the same, the percentage of water is an index : 

 thus, parts having the higher water content are attacked more 

 readily than those with a lower water content.* 



Few will doubt that certain plants have been raised which, 

 so far, are disease resistant, and we must be thankful for 

 these, even if their raising has been brought about by guesswork 

 methods ; there is, however, the fear that when circumstances 

 of climate, soil or moisture are favourable, the disease will 

 reassert itself. In this district the Potato is extensively 

 cultivated and any fact relating to its growth or life history is 

 of interest. 



Some years ago I pointed out to Mr. Massee that the 

 microscopic structure of tubers immune to and those subject 

 to the disease (Phytophthora infestans) differed, inasmuch as 

 the former has much thicker cell walls than those of the latter. 

 Mr. Massee desired me to verify this by growing a number of 

 varieties under the same conditions of soil, climate and moisture, 

 and he sent me some thirty or forty named sets, which were 

 planted and grown in a plot under the same conditions, when 

 further microscopical examination was made confirming my 



* Ohio Exp. Sta. Bull., 214; March 1910. 

 1917 June 1. 



