DISEASES DUE TO BACTEREl, FUNGI AND OTHER LOWER PLANTS I033 



injured. If fumigation is carried out before sunset the pitting is sometimes 

 only found on the sunward side. Finally, if instead of sulphuric acid phos- 

 phoric acid, which is stable and has a very slow reaction is used, the ex- 

 tent of pitting is not in the least reduced nor, as the author ascertained expe- 

 rimentally, is it reduced when chemically pure hydrocyanic acid is employed. 

 It may therefore be concluded with certaint}' that the pitting is caused by 

 hydrocyanic acid and by no other cause. It depends : (i) on the quantity 

 of gas used and the length of fumigation ; (2) on the condition of the plants 

 treated ; (3) on atmospheric conditions. 



Generally speaking, a plant weakened by gummosis, for instance, sus- 

 tains more injury than a vigorous one. The pitting is more severe in fruits 

 with thin skin, especially if the latter has recent abrasions. The Author 

 found that on fruits pricked with a fine needle, then subjected to fumiga- 

 tion with chemically pure hydrocyanic acid, a depressed pitted zone always 

 formed round the prick. Consequently the bulk of the injury arises from 

 lesions occasioned during the pulling over of the tents. 



The pitting is much more severe when fumigation is carried out : i) 

 during hot sunny days ; 2) when the temperature is near 32^ Fahr ; 3) dur- 

 ing exceptionally hot nights ; 4) when a strong wind blows and shakes the 

 tents ; 5) during very wet nights. 



Excessive moisture in itself occasions more injury than all the other 

 factors together, precisely because it renders the tents more impermeable 

 to gas and heavier, which increases the injury already sustained by the trees 

 when they were pulled over. 



The bulk of the injury therefore may be avoided by taking the follow- 

 ing precautions : preventing the tents striking the trees as far as possible ; 

 using poles higher than the trees to support the tents ; stopping the fumiga- 

 tion when the tents are heavy^ with wet or when the trees are wet ; carrjnng 

 out no fumigation during over-hot days, or when windy, or when the tempe- 

 rature is too low (the author advises adopting 36^ F. as the minimum temp- 

 erature) . 



Trees sprayed with Bordeaux mixture may not be fumigated until 

 a year later. Failure to observe this rule causes exfoliation. The Author 

 never found any injury follow from fumigation following treatment with 

 inie and sulphur solution. 



DISEASES DUE TO FUNGI, BACTERIA 

 AND OTHER LOWER PLANTS. 



807 - On the Original Range of Spongospora subterranea. —hYu^N g. r. ami gknek.alitiks 



RCGEkS I.E. in Scituct, New Series, VoL XLII, No. i<jij6, pp. ').|o-<,4i. I,ancaster, I'a., 1916. 



The discovery of Spongospora suhterraiiea by the Department of Agri- 

 culture of the United vStates on potatoes from Peru throws some light on 

 the still unsettled question of the place of origin of this parasite." It is 

 very widespread in Europe, and during the last three or four years has also 



