146 REPRESENTATIVE PLANTS 



Each stiobilus scale is a sporoi)liyll. Examine ((2>) the 

 sporangia borne in the scale axils. How many kinds 

 do you find, and how do they differ? Observe the greeyi 

 sporangium more attentively. What is its form and size 

 when compared with that of the scale? Crush one and 

 observe the large, many-faced spores, megaspores. What can 

 you call the sporangium which produces megaspores only? 

 How many spores do you find in each? Examine the other 

 kind of sporangium. What is its color and comparative 

 size? W^hat markings are on its surface? Crush one and 

 observe the spores. Are they few or many, large or small ? 

 Name the sporangium. In a strobilus try to determine the 

 number of each kind of sporangia. 



Drawings. Make careful drawings of the following : — 



1. A spray of selaginella (natural size). 



2. A portion of stem with leaves (m). 



3. A leaf (Ij^). 



4. A cone (^m), 



5. Mega- and microsporangia (Ip). 

 G. Spores of the two sizes (/p). 



Description. Write a careful description of selaginella 

 or lycopodium. 



Lycopodium is similar to selaginella, but has only one 

 form of sporangium, and there are leaf differences of impor- 

 tance. It may be substituted, but selaginella is the better 

 plant. 



Fossil club mosses. Read about " Lepidodendron " and 

 "Sigillaria" in the reference books. Wliat part did these 

 ancient club mosses have in the production of coal ? What 

 is lycopodium powder ? 



Conclusions from fern-plant study. Evolution. You ought 

 to be able to understand and state the new features intro- 

 duced by the fern-plant classes, i.e., ferns, horsetails, and 

 club mosses. The marked increase in complexity, the inter- 

 esting life history (alternation of generations), and the 



