304 



MORPHOLOG Y. 



Fig. 356. 



end of the ovule. This depression is thus known as the pollen 



chamber. 



618. 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. 



619. 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 begin- 



ning of the female flower to the maturity of the cone, and about 



fifteen months from the time that pollination takes place. 



620. Female prothallium of the pine. To study this we must make care- 

 ful longitudinal sections through the ovule (better made with the aid of a 

 microtome). Such a section is shown in fig. 358. The outer layer of tis- 

 sue, which at the upper end (point where the scale is attached to the axis of 

 the cone) stands free, is the ovular coat, or integument. Within this integu- 

 ment, near the upper end, there is a cone-shaped mass of tissue. This 

 mass of tissue is the nucellus, or the macrosporangium proper. In the 

 lower part of the nucellus in fig. 356 can be seen a rounded mass of "spongy 

 tissue " (spt), which is a special nourishing tissue of the nucellus, or spo- 

 rangium, around the macrospore. Within this can be seen an axile row 

 of three cells (an : m). The lowest one, which is larger than the other 

 two, is the macrospore. Sometimes there are four of these cells in the axile 

 row. This axile row of three or four cells is formed by the two successive 





pfr- 



