THE PLANT GROUPS 135 



B. CONIFERALES (CONE-BEARERS). SPRUCE AND PINE 

 SPOROPHYTE 



1. Habitat (Field study). 



a. What is the nature of the habitat of the spruces and 

 pines of your region as regards soil, drainage, and 

 climate ? Do they grow best on lowlands or on well- 

 drained slopes and uplands? What is the distribu- 

 tion of spruces and pines in the United States ? What 

 is their natural habitat as regards soil and climate ? 

 Are they mesophytic or xerophytic in general habit ? 

 How do you explain the apparent discrepancy between 

 habitat and habit in these trees ? Consult manuals 

 and assigned readings 011 the above points. 



I. Summarize the above points in your notes under habitat, 

 including geographical distribution and habit. 



2. Habit. 



a. Form and body plan of the spruce and pine trees. Eeview 



the text discussion in Part I on the body plan and 

 mode of growth of the spruce and pine trees. Be able 

 to account for the erect conical form, the excurrent 

 trunk, and the false whorls of branches of spruces 

 and pines. Why is the trunk excurrent ? What de- 

 termines the conelike form of the entire tree ? How 

 do the false whorls arise ? Is the entire leafage well 

 exposed to light ? 



b. Summarize the above points under Habit in terms of 



body plan, methods of growth of buds and branches, 

 and tropistic responses of leaves and branches. 

 For a general discussion of the habitat, distribution, and com- 

 mercial importance of the spruces and pines the student should 

 consult the text and figures under Gymnosperms in Part III 

 of text. See also the general map of forest areas (Fig. 223). 



