940 



SCIENCE 



[N. S. Vol. XXVII. No. 703 



ever-present injuries to farm products 

 cause conditions for pathological study. 

 Many diseases are transferred from plant 

 to plant by animals of nearly all classes, 

 and the combined efforts of zoologists and 

 of pathologists will be necessary to combat 

 this evil. Dr. Erwin F. Smith enumerates 

 bees, the potato beetle, snails and slugs 

 as known transportation agents for various 

 diseases. Moreover, we do not yet know 

 how many diseases of animals, both do- 

 mesticated and wild, may be due directly 

 or indirectly to plant diseases. Cases 

 have been reported where serious results 

 lave attended the feeding of diseased 

 fodder to live stock ; and flour, made from 

 infested grain, may cause serious results 

 in man. 



The relations between plant pathology 

 and chemistry are perhaps more intimate, 

 but at first glance less apparent than those 

 already noted. The most obvious connec- 

 tion is through the work which the chemist 

 and the pathologist have done together in 

 developing the manufacture and the use of 

 fungicides. To the farmer, this has seemed 

 the most practical side of pathological 

 work, because of the immediate results in 

 saving crops. A less noticeable but even 

 more important contribution of chemistry 

 is the analysis of soils and of fertilizers, 

 by which we can better know the conditions 

 of optimum growth for various crops, and 

 the best conditions for growing plants 

 which are resistant to disease. The good 

 resulting from this kind of investigation 

 can not be overestimated, for, as a man in 

 good physical condition is able to resist the 

 attacks of many diseases, so a plant, if 

 given the best conditions for growth, will 

 be able to combat the various parasitic 

 organisms which would otherwise destroy 

 it. In another way chemistry will prove 

 in the future a valuable ally in studying 

 plant diseases. In the healthy plant cer- 

 tain products of growth are formed whose 



chemical nature must be known. When 

 the plant is diseased, these organic com- 

 pounds, acted upon by the enzymes pro- 

 duced by the attacking organism, or other- 

 wise changed in composition, must be 

 examined again to determine the nature of 

 the change. 



The relations existing between plant 

 pathology and physics are not so well 

 defined as in the cases already cited. If, 

 however, we keep in mind that there is, 

 in the study of botany, a physical as well 

 as a physiological side, these relations are 

 more easily seen. The ascent of water in 

 trees; the conduction of water, food-ele- 

 ments and foods, and reaction to gravita- 

 tion and to other physical stimuli are 

 problems which the physicist must aid us 

 in solving, though connected with these 

 there are undoubtedly many vital processes 

 which modify the mere physical forces. 

 In a diseased plant the effects of these 

 physical forces are modified probably 

 more than we now realize. We may men- 

 tion as examples of these modifications the 

 stoppage of water-conducting elements in 

 woody plants, the weakening of the tena- 

 city of wood, and similar changes in the 

 physical conditions of plants. 



This is not the place to state more defi- 

 nitely the problems in plant pathology 

 waiting to be solved with the aid of other 

 sciences, but we may note in closing that 

 in the past the interrelations of the sci- 

 ences have not been entirely disregarded, 

 for such men as Pfeffer and Pasteur, by 

 using methods of sister sciences, have made 

 valuable additions to our knowledge of 

 botany. Eenest Shaw Reynolds 



THE AMERICAN ASSOCIATION FOB THE 



ADVANCEMENT OF SCIENCE 



SECTION F— ZOOLOGY 



TEE AMERICAN SOCIETY OF ZOOLOGISTS 



II 



Inhefitance of Comb Form in Poultry: C. 

 B. Davenport, Carnegie Station for Ex- 



