294 MALFORMATIONS AND DISEASES 



424. 



A quite different kind of decomposition is that to which Rye 

 is subject, when it degenerates into davits, which has a great re- 

 semblance to what in German is called the stone blight in Wheat. 

 The grain swells, bends itself, and comes out from its husk. 

 It has a sharp taste, and contains neither gluten nor saccharine 

 matter, but putrid oil, free phosphorous acid, ammonia, and 

 corrupted starch ; (Buchner, Repertorium fur die Pharmacie, 

 b. iii. s. 100.) It is remarkable, that infusory insects, like 

 vinegar eels, are found in it. But whether these were for- 

 merly present, and occasioned the disease of the grain, or 

 were produced by the degeneration, has not been well ascer- 

 tained. Meanwhile it is certain, that very moist yeai's and 

 wet lands contribute in a very great degree to the production 

 ofclavus. 



425. 



Insects occasion a numberless crowd of diseases, and of the 

 causes of death, to plants. Some of these have not yet been suf- 

 ficiently investigated, as the round navel-shaped bodies, which 

 we find in such quantities on our fading Oak leaves, and 

 which, by some authors, are called Xyloma pezizo'ides, and in 

 the Flora Danica (1492), Sclerotium fasc'iculatuvi^ but which 

 have been best examined by Hopkirk, (Flor. Anom. p. 10. 

 tab. XI. fig. 1 .) It is impossible, and it is not indeed suited 

 to our present purpose, to mention all the kinds of injuries 

 which insects occasion to plants. We seek only to present 

 the most important facts, according to the common division of 

 insects. 



Among the Coleoptera we mention, first, the May Bug, 

 (Melolantha vulgaris), the larvae of which are known as 

 grubs, and live four years under ground, where they 

 occasion the greatest devastation among the roots of trees. 

 In their perfect state, too, they lay waste the leaves and buds 

 of orchard and other trees. Equally injurious, but not so 

 common, is the Spring beetle, (Elator Segetis) : the larva con- 

 tinues five years in that state, and is equally hurtful with 

 th€ former kind to the roots of grain ; (Spence and Kirby, 



