PINE 65 



thus apparent in the spring. They are best studied in 

 material collected towards the end of May, at which time 

 the stamens will be opening and the female cones be ready 

 for pollination. The positions which the two kinds of flower 

 respectively occupy on the long shoot bearing them is best 

 defined with relation to the short shoots and lateral long shoots 

 that have been seen above to occupy definite positions. The male 

 flowers take the place of a number of the short shoots at the base 

 of the current year's growth. Each male flower stands in the 

 axil of a scale-leaf. The small cones or female flowers, on the 

 other hand, occupy the place of the large lateral buds at the summit 

 of the shoot ; usually one to three cones are developed on the 

 shoot. Their appearance is represented in Fig. 17, i. 



A single male flower is shown in Fig. 17, 2, on an enlarged 

 scale. The slender stem bears a few scale-leaves below, and 

 further up the numerous closely crowded stamens, which are 

 arranged in a close and complicated spiral. Each stamen is a 

 little leaf with a short stalk widening out into a thin oval blade. 

 This extends almost horizontally from the stem of the flower, 

 but the pointed tip bends upwards. Hanging down from the 

 horizontal portion is a pair of pollen sacs. These when young 

 are protected by the terminal portion of the stamen below. 

 When the flower is mature its stem lengthens slightly, thus 

 separating the stamens. Each pollen-sac then opens by a longi- 

 tudinal split shown in the figure, and the yellow pollen readily 

 escapes. On touching a branch with mature male flowers this 

 comes out in a dusty yellow cloud. The pollen grains are peculi- 

 arly constructed to render them especially buoyant, but this can 

 only be seen with a compound microscope. It will be clear, how- 

 ever, that abundant pollen is produced and that it is well suited 

 for wind-pollination. 



One of the young female cones or flowers is shown similarly 

 enlarged in Fig. 17, 3. In colour it is usually pink or purplish 

 red, sometimes greenish. At the base of the rather stout stem 

 are a few scale-leaves, and above this come the structures bearing 

 the ovules. These are most simply regarded as leaves, and com- 

 pared with the carpels of the flowering plants we have studied. 

 Each consists, however, of two parts, a small pointed scale-leaf 



VOL. IV. 5 



