1897.] PUBLIC DOCUMENT — No. 33. 57 



REPORT OP THE BOTANISTS. 



GEORGE E. STONE, RALPH E. SMITH. 



TliP work of this tkpartment has followed the plan out- 

 lined in the last annual report. Much of our attention dur- 

 ing the past year has been devoted to the study of the 

 gall-forming nematode worms aftecting cucumbers and to- 

 matoes grown under glass, in the hope of finding some 

 eftectual method of combating them. Professor Smith has 

 devoted considerable attention to the study of their life his- 

 tory. The results of the investigations, when completed, 

 will be published in a bulletin. 



Most of the correspondence of the department has had 

 reference to plant diseases, although during the summer 

 many inquiries have been received regarding weeds. For 

 the purpose of facilitating their study, we have collected 

 during the past summer about two hundred and fifty species 

 for the herbarium, including several species which have been 

 recently introduced in grass and other kinds of seed. The 

 department takes this opportunity of soliciting correspond- 

 ence on this subject, as it is desirous of obtaining information 

 in regard to the introduction and distribution of weeds and 

 other plants which may possibly become troublesome. ' 



The Nature of Plant Diseases. 

 Before passing on to a consideration of some of the plant 

 diseases which have occupied our attention during the past 

 year, it will be well to pay some attention to the nature of 

 plant diseases in general. The diseases with which botanists 

 have to deal can be divided into two classes, namely : first, 

 those which are caused by parasitic fungi, bacteria and simi- 

 lar organisms ; and second, those brought about by purely 

 physiological disorders, which have their origin in some ab- 



