202 STUDY OF COMMON PLANTS. 



Note. — Like many other facts usually treated as morphological, the 

 character of the inflorescence is of much physiological importance. 

 The successive opening of the flowers in regular order, instead of simul- 

 taneously, insures a much longer period of time during which fertilization 

 may take place, and their position and aspect when ready for pollination 

 are most frequently such as to render them conspicuous and easily acces- 

 sible to insect visitors. The latter, while gathering honey, are often 

 observed to proceed in a methodical manner corresponding to the order 

 of development of the flowers. 



Flower. 



I. Study the structure and plan of the flower. Is it 

 perfectly regular ? 



Note . — Give special attention to this point. The beginnings of irregu- 

 larity are of great interest, since they give us a clue to the way in which 

 some of the most efficient mechanical contrivances in the vegetable king- 

 dom have originated. 



II. Study next the ovary. 



1. Cut transverse and longitudinal sections of ovaries of 



various ages. 



2. Make out the form and place of attachment of the 



ovules. 



3. In the partially developed fruit examine the imma- 



ture seeds, and note the form and position of the 

 embryo, easily recognized by its green color. 



4. Construct a diagram of the flower. 



Physiological adaptations. 



I. Examine with a good lens the surface of stem, leaves, 

 flower-stalk, and calyx. Are there any distinctively pro- 

 tective arrangements? 



II. In what ways is the inflorescence adapted to cross- 

 fertilization? Notice the position of the open flowers as 

 contrasted with that of the flower buds. Effect of " mass- 

 ing." 



