SECTION X. ANGIOSPERMS (DICOTYLEDONS) 



SPOROPHYTE 



Examine typical dicotyledons in the laboratory and in the 

 field, and review previous work on dicotyledons such as beans, 

 mandrake, locust, and elm. Determine as follows the distinc- 

 tive characteristics of dicotyledons which distinguish them 

 from Pteridophyta and gymnosperms. 



1. Habitat. What is the prevailing habitat of dicotyle- 



donous plants of your region ? Be able to name some 

 mesophytes, xerophytes, and hydrophytes among them. 

 Is your region typical for the habitat of dicotyledons in 

 the United States ? Consult the text under Descriptive 

 Terms for figures and the meaning of terms used below. 



2. Habit (geranium and similar dicotyledons). 

 a. Leaf form and venation. 



(1) Compare the leaves of dicotyledons with those 



of Pteridophyta and gymnosperms, including 

 spruces and pines. Are the dicotyledons large 

 leaved as a group ? What terms describe the 

 form, margin, apex, and base of the leaves you 

 are examining? Consult Fig. 208 of text. 



(2) Hold a leaf toward the light and study the venation. 



Is it pinnately or palmately veined ? Do the veins 

 end free in the margin (open venation) or are 

 they united (closed venation) ? See text, p. 415. 



(3) /Structure. Review the structure of leaves in Chap- 



ter VI of the text in connection witli Fig. 208. 



3. Anatomy (herbaceous type, for example, geranium). Re- 



view the structure of herbaceous stems in Part I of 

 143 



