699 



Of the unusually numerous practical experiments made especially by 

 Smith^, it can be only stated as a result, that no one has succeeded, as yet, 

 in obtaining any indication of the cause. In ordinary years, a lack of nutri- 

 tion, or its excess, can not be considered as a reason for the disease. Still it 

 may be observed that rainy, cool summers show a decrease of the disease 

 and dry periods, an increase. Grafting on the Marianna plum was found 

 to be apparently a protection against the rosette disease, since the eyes from 

 the diseased peach developed to healthy shoots. Infection experiments with 

 about twenty different kinds of bacteria and yeasts, taken from the tissue of 

 diseased peaches, gave no other result than a swelUng in a few cases at the 

 point of infection or an exudation of gum-. 



The almond suffers from both of these diseases and apricots and Japa- 

 nese plums from the yellows^. 



In my opinion, injuries are concerned here which are produced by 

 intensive cultivation and lack of consideration of the soil requirements of 

 the peach. In the long run, all heavy soils, rich in fertilizers, become 

 dangerous for the peach. In combatting this disease, it might be well to 

 consider primarily cultivation on light soils and in open places. 



GUMMOSIS OF THE ChERRY. 



The exudation of gum is well known as a widespread phenomenon 

 especially among the stone fruits and can be produced by very different 

 kinds of causes. 



With us, the cherry and the peach suft'er most frequently from gum 

 exudations. We sometimes find light yellow, transparent masses, at other 

 times brown, cloudy solid ones, extending over a part of the bark of a 

 branch or the trunk. These masses are soluble in boiling water; insoluble 

 in alcohol and cannot be crystalized. When boiled with dilute sulfuric acid, 

 the jam contains a sugar which can ferment and yields mucic acid when 

 treated with nitric acid. They belong, therefore, to that group which 

 organic chemistry terms Gums. Different varieties of gums have been dis- 

 tinguished, according to their capacity for swelhng in water. Gum per- 

 fectly soluble in cold water is called Arahin, which has all the characteristics 

 of an acid*. The gum tragacanth which swells up in water to a sticky jelly 

 is a representative of the Bassorin group, and the modification of Bassorin 

 is called Cerasin, which is soluble in boiling water. Cherry and plum gums 

 are a mixture of Arabin and Cerasin. We may assume that the gum formed 

 in gummosis changes its constitution according to the time of its production 

 and the character of the tissues from which it is produced. It may have 

 some relationship with pectin substances. Gum arable has the character of 

 an organic calcium salt. 



1 Smith, E. F. Experiments with fertihzers, etc.; cit. Zcitschr. f. Pflanzenkr. 

 1R94, p. 177. 



2 Smith, E. F. Additional notes on peacli rosette. The .Tournal of Mycology, 

 Vol VII, No. 3, 1893. 



•T Cit. Zeitschr. f. Pflanzenkr.nnkh. 1S9G, p. ir)6. 



4 Czapek, Fr. Bionhemic d. I'flanzen. I.eipzig-, 190;", Vol. T, p. .'irid. 



