DISEASES OF CROPS. 



sexes. The reproduction of insects is essentially oviparous 

 (producing eggs), some are ovo-viviparous {i.e., the eggs 

 are hatched and the young developed to a greater or 

 less extent ivithin the body of the parent), and a few 

 {Aphides) are viviparous (producing living young) at 

 certain periods. The ravages of insects, which sometimes 

 occasion such serious panics, are explained by their enor- 

 mous fecundity. Sir Richard Owen, K.C.B., F.R.S., 

 estimated that a single Aphis in the tenth generation 

 produced no less than 1,000,000,000,000,000,000 (a quin- 

 tillion) young (Owen's " Invertebrata," p. 44). 



We propose to arrange the subject matter of this book 

 under the following headings :— 



(a) The Diseases of Leguminous crops. 



(/3) The Diseases of Root crops. 



(y) The Diseases of Gramineous crops. 



(8) The Diseases of Miscellaneous crops. 

 In each case the diseases produced by the members of 

 the animal kingdom will be described first, and the fun- 

 goid diseases afterwards. 



The subject of nomenclature throughout this book is 

 not thoroughly " orthodox," and may possibly awaken 

 some controversy. As every scientist has his own views 

 on this subject, the author may be permitted to have his. 

 Concerning the nomenclature used it will be noticed that 

 no describers' names are appended to the species described. 

 Thus Anthomyia Brassicce, Bouch6; Tipula oleracea, 

 Linnaeus ; Peronospora Vicice, Berkeley ; Peronospora 

 trifoliorum, De Bary, etc., become : Anthomyia Brassicce ; 

 Tipula oleracea ; Peronospora Vicim ; Peronospora 

 trifoliorum, etc. 



The late Mr. Darwin was averse to the " orthodox " 

 system of nomenclature, as the following quotations from 



