PREFACE. 



Ever since the epoch-making- discoveiy of Charles Darwin there has 

 been a steadily increasing- influence of the theory of evolution on the 

 scientific study and practical utilization of the plants and animals on 

 which agriculture is based. The present paper marks a step in 

 the further working out of the doctrine of descent, inasmuch as it 

 embodies results of an association of the data won in two ver}^ different 

 fields of investigation; one making the cell its object of study, the 

 other occupied with the species. The results herewith presented open 

 new views as to the nature of higher animals and plants which can 

 not fail to stimulate research and which promise to have great 

 economic significance in the determination of the actual and latent 

 capacities of the organisms utilized by man. 



A. F. Woods, 

 Pathologist and PJiysiologist. 



Office of Vegetable Pathological 



AND Physiological Investic^ations, 



Washinyton, D. 6'., May 8, 1905. 



