are not commonly recognized, and which require a high 

 degree of special botanical training. The necessity of 

 botanical knowledge in the use of plants and their prod- 

 ucts in the arts, or as drugs, is easily understood without 

 further reference, and such uses do not necessarily involve 

 any broad knowledge of plants as a whole. 



It is quite different, however, in the matter of plant 

 pathology, for here every channel of botanical informa- 

 tion must be used to investigate plant ailments. Bacteria 

 and parasitic fungi, which are themselves plants of a low 

 order, are the cause of the bulk of plant diseases and for 

 that reason the study of their life histories becomes a mat- 

 ter of no small importance. Then, too, the structure and 

 habits of the host plants must be taken into consideration, 

 for upon these may depend the means of prevention or of 

 cure. The assembling of this information and its prac- 

 tical application to the question in hand devolve upon that 

 type of botanist usually referred to as the mycologist, 

 and despite many failures much that is of substantial 

 practical use has been established. One of the earliest, if 

 not the earliest, recorded instances of where a community 

 has taken formal notice of the fungus pests of plants is 

 found in the old Barberry Law passed by the province 

 of Massachusetts before the Revolution. This called for 

 the extirpation of the barberry which had been noticed by 

 the colonists, without any knowledge on their part of the 

 real cause, to be connected with the rust of their wheat 

 fields. Today we may not pass laws for the destruction 

 of diseased plants, realizing perhaps the hopelessness of 

 enforcing them, but we combat plant disease by the estab- 

 lishment of experiment stations devoted to the investiga- 

 tion of such matters. 



As a result, there is now at the disposal of the agricul- 

 turalist much definite information of ways and means of 

 diminishing or preventing loss through the destruction of 



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