DISEASES OF VEGETABLES. 287 



moist state of the air at seed-time. An acute observer 

 in this country thinks it is sometimes occasioned by 

 late frosts, which occasionally affect the plants so as to 

 cause this malformation of the grain. The general 

 opinion is, however, that it is really a fungus, which, 

 seating itself within the husk, changes the meal into 

 grey powder. Several others of the Graminece are 

 subject to ergot. The Lblium perenne, Festuca 

 hordeiformis, and Elymus maritima, are frequently 

 seen disfigured by it ; on the Lblium it is black, and 

 on the Etymus, red. 



Constriction of the Bark. This is a defect in the 

 growth of trees, occasioned by the diminished powers 

 of the root, or from the desiccating effects of dry or 

 cold air on the branches. It has been already observed, 

 that the bark is an excrementitious part of the plant. 

 Nature intends, that as a new bark is every year 

 formed next the wood, the outer or first formed layers 

 should either be gradually thrown off, as in Platanus, 

 stretched horizontally, as in the beech, or rifted longi- 

 tudinally, as in the oak, to make room for the new 

 accretion within. If, however, from any cause the 

 outer bark becomes unnaturally indiirated, so as to 

 lose its expansive property, the internal growth is 

 confined, and all the functions of the tree are para- 

 lised. Hence it remains stationary, the prey of insects, 

 moss, lichen, and rarely fruitful ; in which state it is 

 said to be hidebound. 



The old remedy for this defect was scoring the 

 stem and branches from top to bottom quite through 



