NOTES AND ABSTRACTS. 



287 



" Academie des Sciences " from which it appears that the anatomical 

 examination of grafts of Helianthus on Helianthus and of Opuntia on 

 various Cacti has revealed to him the existence of internal adventitious 

 roots formed in the stock and penetrating to varying depths in its 

 tissues. Occasionally these roots even reach the soil and bestow 

 complete independence on the graft. M. Daniel considers this to be 

 the probable explanation of certain cases of hybridization through 

 grafting.— M. L. H. 



Grapes, Black Rot Disease of. By Donald Reddis (U.S.A. 

 Exp. Stn., Cornell, Bull. 293 ; 1912). 



Guignardia Bidwelli, Black Rot, so called to distinguish it from 

 grey and brown rots due to mildews, &c, is one of the worst diseases 

 the wine-grower has to contend with. 



All green parts of the plant are attacked, showing reddish-brown, 

 more or less circular spots. The spots on the young berries increase 

 rapidly in size, a thin superficial crust appears, and the whole berry 

 may become involved. 



Pycnidial, spermagonial, and perithecial stages occur. The peri- 

 thecia, containing many asci, form the resting stage, and can develop 

 at very low temperatures as long as there is sufficient moisture 

 present. The ascospores infect the young leaves and green portions 

 of the plant. 



The author has found through experience that every infection of 

 any consequence is directly traceable to meteorological conditions, 

 rain of some duration, or rain followed by fog. The spores of the 

 fungus are discharged by a mechanical process, in the presence of 

 precipitated moisture only. Moisture is also necessary for the germina- 

 tion of the spores. Bordeaux mixture has been found to give the best 

 results. Spray before rain if possible. 



Many good figures are given, together with an extensive biblio- 

 graphy.— £>. M. C. 



Heather, Biology of. By M. C. Rayner (New Phytologist, xii. 

 59-77 ; 1913 ; 1 plate, 2 text figs.). — While this paper is largely of 

 ecological interest and refers to the investigation of the common 

 heather (Calluna vulgaris), some of the interesting results obtained by 

 the authoress may well prove to be of general application to Ericaceae 

 and other plants with a mycorrhiza. While the heather is usually 

 recorded as forming definite heath communities, in competition with 

 other plants, only on poor and often acid soils, sporadic communities 

 of this plant were found on the higher parts of the downs in Wiltshire 

 and Berkshire, forming patches of typical heath vegetation. The 

 soil monopolized by the heather was found to be in all respects a good 

 fertile loam, with a high percentage of available mineral matter ; apart 

 from the low percentage of calcium carbonate, there was no evident 

 factor to account for the successful competition of the Calluna on this 

 somewhat unusual substratum. The object of the investigation was 



