Vlll PREFACE. 



siderable space has been devoted to its appliances and 

 methods. This special treatment has been supplemented 

 by a series of practical exercises which the student is 

 urged to perform in the order designated. It will be 

 seen that in some cases several examples are suggested : 

 the beginner is advised to examine thoroughly at least 

 one of the examples under each head. 



Organogeny, the study of nascent organs, occupies much 

 of the middle ground between Histology, Morphology, and 

 Physiology. The means by which it is investigated are 

 those of Histology, but its answers are given to Mor- 

 phology. For convenience, the study of the development 

 of each organ of the plant is made to precede the examina- 

 tion of its mature state. 



Vegetable Physiology concerns itself with the life of 

 plants. The appliances of which it makes use are taken 

 chiefly from Physics and Chemistry, and facility in their 

 employment demands some practical acquaintance with 

 those departments. To one who has worked systemati- 

 cally in a physical and chemical laboratory, experimental 

 vegetable physiology presents little difficulty. To aid the 

 work of students whose opportunities for experimenting 

 in Phvsics and Chemistry have been slight, a series of 



4/ *f 



practical exercises in Experimental Physiology has been 

 added. The appliances selected for these examples are 

 not complicated or expensive, and it is hoped that teachers 

 and students alike may find their emplo3anent practica- 

 ble. The Praxis embodies in compendious and conven- 

 ient form the directions which have been employed by 

 the author in his classes. 



The illustrations of tissues and of apparatus have been 

 taken from many sources. They have been selected with 



