290 Frederich Stoward : 



Streiig:th of acid Phytophthora in/entans, De Bary. 



0.0049 per cent and inalt extract Coiiidia, an injurious effect 



is evident 



0.0098 per cent and malt extract Conidia, absolutely no ger- 



minative processes take 

 place 



0.0049 per cent - - - Zoospores, motility of spores 



immediately arrested, 

 germination suppressed. 



The amount of acid which diffuses into the treated undamaged 

 tuber, calculated as a percentage on total weight of tissue is 

 0.089 per cent. In the case of blight-infected material, the per- 

 centage absorbed is certainly higher. In either case, the diffused 

 acid is distinctly localised and consequently in those portions 

 of tissue into which it has penetrated the percentage will be 

 greater than the above value. 



In view of Wiitrich's observations, the death of the fvmgal 

 mycelia after the treatment of blight-infested tubers, with 10 

 per cent, acid is therefore easily conceivable. 



Summary. 



The results embodied in this paper may be briefly sum- 

 marised : — 



(1) When intact, blight free, mature tubers are steeped 

 in aqueous solutions of the \ arious chenucal substances 

 enumerated in this paper, the entry of the solute 

 during the earlier stages of immersio)! is chiefly if not 

 solely via the buds of the tuber. 



(2) A steep of 10 hours' duiation in a 10 [)er cent, 

 solution of >iqueous sulphuric acid sutiices to destroy 

 the vitality of the buds of the tubej-s, steeped in this 

 reagent. 



(3) A steep of 10 hours" dui-ation in a 10 per cent, 

 solution aqueous sulphuric acid suffices to destroy the 

 vitality ot the buds and also that of the fungal 

 mycelia in the case of blight infested tubers. The 

 solute in this case not only enters via the buds but 



