286 



THE SUGAK BEET. 



quently obstructing the respiratory organs of the sickly 

 leaves of plants.^ 



Fig. 77. 



Fig. 78. 



Fig. 79. 



Fig. 77. — The malady has penetrated through the radicle, causing a total loss 

 of the spongiole. 

 Fig. 78. — One of the vessels of the vascular tissue in perfect health. 

 Fig. 79. — One the vessels of vascular tissue suffering from disease. 



The fig. 78 represents one of the vessels of the vas- 

 cular tissue in a perfect condition of health. The fig. 

 79 represents the same when attacked, and, as can be 

 seen, the disease seems to have penetrated by degrees 

 the elliptical openings. 



Payen^ says this brown organic substance resists 



' Our intention had been to make these experiments, but we have not as yet 

 had the leisure. 



^ Mr. Payen and others, in 1851, spoke of methods adopted to prevent the 

 above disease, which are to make use of chemical fertilizers. Fifteen years later 

 he acknowledges that if these be used in excess they may be the direct cause ot 

 the disease. The last hypothesis we consider the most rational. 



