6 PLANT PHYSIOLOGY 



not be denied that modern cytology is interesting itself very 

 much in function, but the main interest is in form, and the func- 

 tional aspects of their subject have been taken over by the phys- 

 iologists and the geneticists. 



Histology or minute anatomy is the study of the tissues and 

 their relations to the cells on the one hand and to the organs on 

 the other. At present histology courses are largely courses in 

 technique rather than in the actual tissues themselves. Gross 

 morphology is that branch of morphology which treats of the 

 relations of the plant organs to the plant organism as a whole. 

 A large part of elementary botany is gross morphology. 



Turning now to systematic botany, we see that it also has 

 two main divisions, — taxonomy and paleobotany. The former 

 concerns itself with the classification of extant plants and en- 

 deavors to show by a study of their structures their relation- 

 ships to each other in the evolutionary scale. Paleobotany, on 

 the other hand, tries to solve the problems of phylogeny and evolu- 

 tion by studying extinct forms, which exist to-day only as fossils. 



This serves to delimit the provinces of morphology and sys- 

 tematic botany, but there exists a special field connecting them 

 in which the emphasis is placed with equal stress upon form per 

 se and form for the sake of determining relationships. This field 

 known as comparative morphology is hence a connecting link be- 

 tween systematic botany and morphology. The workers in this 

 field have divided up the territory in accordance with the great 

 divisions of the plant kingdom and call themselves algologists, 

 mycologists, bryologists, etc., depending upon their special in- 

 terests. 



Functional Studies. — Among the subjects which deal with 

 the functions of plants, there are two main divisions,— physiology 

 and ecology. The former considers the function, operation, and 

 behavior of plants when grown under experimentally controlled 

 conditions in the laboratory, as contrasted with ecology, which, 

 in general, considers the behavior of plants out of doors in their 

 natural environment, but here also the two fields overlap con- 

 siderably. 



This much is sufficient to define in general terms the great 

 divisions of the so-called "pure" botanical sciences, but just 

 as we have seen that morphology and systematic botany are 

 connected by a series of intermediate subjects, in like manner 



