PINTJS LARICIO 167 



illustration of the modification of organs for various 

 functions. 



3. Enumerate all the homologs of the foliage-leaf 

 found thus far on Pinus, and show why the organs 

 you name are homologous. 



REPRODUCTION 



F. The Staminate Cone: 



1. On which portion of the vegetative branch are the 

 staminate cones borne? Do they extend clear to 

 the tip of the branch, i.e., are they ever terminal? 

 In what does the tip of the branch that bears 

 them terminate? Ascertain their length and 

 greatest diameter in millimeters. 



2. Are the cones subtended by (i.e., borne in the axil 

 of) a scale-like leaf? Note whether they are sessile 

 or stalked? 



3. Observe the spiral-like arrangement of the micro- 

 sporophylls of the cone. 



4. The staminate cones are modified branches. To 

 which of the vegetative branches are they homolo- 

 gous? 



5. Make a diagram (X 2) showing the mode of attach- 

 ment of the cone and the subtending scale. 



6. With a razor bisect a cone longitudinally and ob- 

 serve the central axis, bearing the microsporophylls, 

 or stamens. 



7. With the aid of a hand lens, or dissecting micro- 

 scope, observe the short stalk of each stamen and, 

 on the under (dorsal) side of the broadened stalk, 

 two small pouches, the pollen-sacs (microspor- 

 angia), containing pollen-grains. 



8. Make a diagram (X 10) of the cone as seen in longi- 

 tudinal section. 



