GYMNOSPERMS. 193 



a sticky fluid in this depression between the curved processes at 

 its lower end. The pollen sticks to this, and later, as this viscid 

 substance dries up, it pulls the pollen close up in the depression 

 against the lower end of the ovule. This depression is thus 

 known as the pollen chamber. 



Now the open scales on the young female cone close up 

 again, so tightly that water from rains is excluded. What is 

 also very curious, the cones, which up to this time have been 

 standing erect, so that the open scale could catch the pollen, 

 now turn so that they hang downward. This more certainly 

 excludes the rains, since the overlapping of the scales forms a 

 shingled surface. Quantities of resin are also formed in the 

 scales, which exudes and makes the cone practically impervious 

 to water. 



The female cone now slowly grows during the summer 

 and autumn, increasing but little in size during this time. 

 During the winter it rests, that is, ceases to grow. With the 

 coming of spring, growth commences again and at an accelerated 

 rate. The increase in size is more rapid. The cone reaches 

 maturity in September. We thus see that nearly eighteen 

 months elapse from the beginning of the female flower to the 

 maturity of the cone, and about fifteen months from the time 

 that pollination takes place. 



Material. everal branches of the pine showing the long shoots and 

 whorls of branches. (These should be had in the laboratory if the tree can- 

 not be studied in the open. If fresh branches cannot be had, preserve them 

 dry.) 



Mature cones collected in August just before the seeds fall away. 

 Branches with the female cones, collected from the top of the tree, in early 

 summer (June), preserve in alcohol. 



Branches with the clusters of male cones collected late in May or early in 

 June just before the pollen is scattered. Preserve in alcohol. 



Sections to show the female prothallium, archegonium, and fertilization 

 can be made by the teacher, or they may be purchased of supply companies. 



Dissecting microscope, or tripod lens ; dissecting needles. 



