376 NOTICES OF BOOKS AND MEMOIRS. 



labelled " Lepidium petrmtm, Ingleborrow, Mr. M'B [itchie] " ; and 

 Mr. Baker (' Journ. Bot.,' iii., 92) mentions one in his possession 

 which had been received from Mr. Caley in 1790. No further 

 evidence has been brought forward in support of the claims of 

 Hutchinsia alpina to a place in our Flora; but it may be worth 

 while to place on record that in the private collection of Eobert 

 Brown (formerly in the possession of Mr. J. J. Bennett) which is 

 now being incorporated in the National Herbarium, there is a 

 specimen of the plant labelled, " Lepidium alpinwn. Hudson, 

 Anglia." — James Britten. 



iExttracts anil Notices of ftoofts aitir jDfcmoirs* 



THE DIFFUSION OF THE CONIDIA OF PHYTOPIITHOEA 



INF E STAN S, De Baot. 



[From the Keport of the Evidence given before the Select Com- 

 mittee of the House of Commons on the Potato Crop, which has 

 lately been issued, it appears that two different opinions were 

 maintained as to the mode of the diffusion of the conidia of 

 the above-named fungus. Mr. Dyer, who was supported in his 

 opinion by Prof. Baldwin, of the Agricultural Department of the 

 National Board (Ireland), believed that this takes place by such 



farm 



manure 



been used in another/' and that the atmosphere was not effective 

 as a mode of communicating the disease. Mr. Carruthers, on 

 the other hand, held that the disease was usually spread by the 

 atmosphere. " If you have a condition fit for the growth of mould 

 of cheese or any decaying matter, you will find spores present in 

 the atmosphere ready to take advantage of this condition of things, 

 and the mould will at once make its appearance ; and so it is with 

 this mould of the potato," Mr. Worthington Smith and Dr. 

 Voelcker agreed in this view ; and Mr. George Murray, in a letter 

 (printed as an Appendix to the Eeport) to the Chairman of the 

 Committee (Major Nolan), recounted an experiment which seems 

 to prove the correctness of Mr. Carruthers' judgment. He has 

 given us the following account of the experiment, with several details 

 not included in the above-mentioned letter.] 



"In the middle of August, 1876, I instituted the following 

 experiment, with the object of determining the mode of diffusion 

 of the conidia of Phytophthora infest am. 



"The method of procedure was to expose on the lee side of a 

 field of potatoes, of which only about two per cent, were diseased 

 ordinary German microscopic slides, measuring two inches long by 

 one inch broad, coated on the exposed surface with a thin layer of 

 glycerine, to which objects alighting would adhere, and in which, 

 if of the nature of conidia, they would be preserved in a condition 

 suitable for examination. These slides were placed on the pro- 

 jecting stones of a dry-stone wall which surrounded the field, and 



? 



