76 MORPHOLOGY AND LIFE HISTORY 



(e) Make drawings showing all features shown 

 under 2, (b)-(d). 



(/) Describe a cross-section of a pinna as shown in 

 a prepared slide. Draw. Compare its struc- 

 ture with that of a foliage-leaf of a higher plant. 

 E. Non-sexual Reproduction: 



1. Describe the possibilities of vegetative propagation 

 of the sporophyte. 



2. With a needle remove several sporangia from a 

 sorus, mount them in water and study under low 

 power. 



3. Observe the differentiation of the sporangium into 

 a stalk (pedicel), and a spore-case, containing 

 spores. Note the walls of the spore-case, and the 

 row of thickened cells, the annulus. Describe these 

 cells. Note the special place for opening of the 

 spore-case, through which the spores escape between 

 the lip-cells. 



4. Make a drawing of the sporangium, about 35 mm. 

 in shortest diameter, showing a portion of the 

 pedicel. 



5. Study the shape and surface markings, if any, of 

 a single spore. Account for the shape. Are they 

 all of substantially the same size, i.e., isPolypodium 

 a homosporous pteridophyte? 



6. Make a drawing of the spore 15 mm. in longest 

 measure. 



7. Run a drop of glycerine under the cover-glass and 

 carefully watch for the snapping motion of the 

 sporangia by which, in nature, the spores are 

 expelled. 



8. Explain the advantage to the species of having the 

 spores Expelled. Why would it not be as well if 

 they merely dropped out of the spore-case? 



