314 ON THE MATURATION OF GRAIN 



botanists term the dienchyma of the leaves. It 

 is at first a mere discoloration ; and never shows 

 itself until the axis of growth and the leaves have 

 acquired their full expansion. It appears, hence, 

 a diseased state of the juices of the leaves. This 

 speck of discoloured fluid spreads within the 

 cellules, until it reaches the nearest stomata or 

 breathing pores, on the under disk of the leaf. 

 Immediately after reaching the pores, the mycelium 

 of the Botrytis Solani of Hartig (the B — infestans 

 of Berkley and others) shows itself on the under 

 disk. And as a Botrytis can only germinate in 

 morbid alkaline matter, its presence indicates 

 that the discoloured fluid is of an alkaline nature. 

 A black blotch now becomes visible externally, 

 and spreads itself rapidly along the substance of 

 the leaf. The cellules themselves are dissolved 

 by the gangrenous fluid, and in a few days the 

 whole leaf falls in a deliquescent mass. If it falls 

 upon the haulm in this state, the virulent matter 

 blisters the epidermis of the haulm ; but as, at 

 this period of the haulm's growth, it contains no 

 stomata or breathing pores — no fungus appears ; 

 and the fibrous tissues beneath the epidermis, 

 not being soluble in the virulent fluid, the morti- 

 fication is not communicated to the haulm — but 

 being bereft of 'ts leaves, and its natural supplies 



