PROCEEDmGS 



OF THE 



HEKTFORDSHIKE ]>^ATURAL HISTORY SOCIETY. 



Bye MEETiyG, 22nd October, 1891, at St. Albaijs. 



The study of plant -diseases and of injuries to plants, caused by 

 fungi and insects, being of considerable economic importance, and 

 attracting much attention at the present time, the President of the 

 Society and Mrs. Hopkinson invited the members and their friends 

 to a second " Evening with the Microscope"* at their residence, 

 The Grange, to examine plants injuriously affected and to discuss 

 some of the many interesting points connected with the subject. 



Microscopes with which to view the minute fungi parasitic upon 

 the leaves, etc., of the higher plants, were brought by several 

 members, and many interesting objects were thus examined. These 

 were chiefly from Mr. Hopkinson's collection and fi'om a collection 

 sent by Mr. R. T. Andrews of Hertford, the former being trans- 

 parent, for examination by transmitted light, and the latter being 

 opaque, for reflected light. Unmounted leaf-fungi sent by Mr. 

 "NVatson "Walker were also examined microscopically. 



Injuries to plants caused by insects were illustrated by a num- 

 ber of diagrams executed and lent for exhibition by the Misses 

 Ormerod. These diagrams represent the insects in their natural 

 size and magnified, show the nature of the injuries they cause to 

 our field- and garden- crops, and give the remedies for each attack. 



Plants, also, injured in vaiious ways, were sent by Mr. J. "W. 

 Odell. These included pieces of apple-stems showing injury by 

 American blight or woolly aphis ; leaves and fruit of the tomato 

 affected with Peronospora infestans ; leaves of Chrysanthemum with 

 mildew ; leaves of cabbage with white rust ( Cystopus candidiis) : 

 leaves of Metia, a ten-estrial orchid from China, with rust ; swede 

 turnips diseased with "club-root" {Flasniodioj^hora hrassicce) ; 

 fasciated stems of Pyrethrutn idiginosum ; and three different forms 

 of Celosia cristata — (1) the normal form, (2) the half-fasciated 

 foi-m, and (3) the "cock's comb" form, a fasciated inflorescence 

 which florists have fixed by selecting time after time the more 

 fasciated forms. 



* The first "Evening" was devoted to the study of the eyes of insects. See 

 ' Transactions,' Vol. V, p. xxxx'i. 



VOL. VII. — PART VIII. B 



