xxxvi.] POTATO DISEASE, II. PASSIVE STATE. 315 



potato tuber is decomposed, and it is impossible to replace 

 rotten tissues with sound. With the object of prevention 

 in view, hardy varieties which have not exhibited disease 

 should be selected and reselected. They should be grown 

 where possible in well- drained dry soil, and mineral 

 manure should be used. As darkness, heat, and humidity 

 are highly favourable to the growth of the Peronospora, 

 all potatoes should be stored in perfectly dry, airy places, 

 in positions where light is not entirely excluded. Potatoes 

 should never on any account be stored in heaps or in the 

 damp holes in the ground termed " pies." 



During the last year or two great attention has been 

 directed to the potato plant and its treatment under 

 disease, chiefly by Mr. J. L. Jensen of Copenhagen, and 

 Mr. C. B. Plowright, M.K.C.S., in the pages of the 

 Gardeners' Chronicle, and more lately by Mr. J. G. Baker, 

 F.R.S., in the Journal of the Linnean Society, and to these 

 communications it is necessary for us to advert. 



The paper by Mr. J. G. Baker, F.K.S., F.L.S., written 

 at the request of Earl Cathcart, in the Journal of the 

 Linnean Society (" Botany," vol. xx. p. 489), is called " A 

 Review of the Tuber-bearing Species of Solanum" Mr. 

 Baker reviews the species and varieties of tuber-bearing 

 Solanum geographically, beginning under Chili with 1. 

 Solanum tuberosum, L. ; 2. S. etuberosum, Lind. ; 3. S. 

 Fernandezianwn, Phill. ; 4. S. Maglia, Sch. ; and 5. S. 

 Collinum, Dun. Brazil 1. S. Commersoni, Dun., and its 

 var. S. Ohrondii y Carr. Peru, Bolivia, Ecuador, and 

 Colombia 1. S. tuber osum, L. ; 2. S. immite, Dun. ; 3. 

 S. Colombianum, Dun. ; 4. S. Valenzuelce, Pal. (S. Maglia 

 Sch.) Mexico 1. S. verrucosum, Sch. ; 2. S. suaveolens, 

 K. and B. ; 3. S. stoloniferum, Sch. ; 4. S. demissum, Lind. ; 

 5. S. utile, Klot. ; 6. S. squamulosum, M. and G. ; 7. S. 

 cardiophyllum, Lind. ; 8. S. oxycarpum, Sch. South- West- 

 ern United States 1. S. Fendleri, A. Gray ; 2. S. Jamesii, 

 Torr. Of these plants Mr. Baker considers there are only 

 six genuine species in a broad sense, viz. 1. Solanum 



