304 



MORPHOLOGY. 



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 tliis 

 time have been standing erect, so that 

 the open scale could catch the jjoUen, 

 now turn so that they hang downward. 

 This more certain!)' excludes the rains, 

 since the overlapping of the scales forms 

 a shingled surface. Quantities of resin 

 are also formed in the scales, which 

 .an exudes and makes the cone practically 

 impervious to water. 



619. The female cone now slowl}' 

 grows during the summer and autumn, 

 increasing but little in size during this 

 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 oi a 

 microtome). .Such a section is shown in fig. 35S. 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 nucelUis^ or the niaerosporangiuni proper. In the 

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

 tissue *' (.?/*/), wlilch is a special nourishing tissue of tlie nucellus, or spo- 

 rangium, around the lluuTospore. Within this i.m be seen ati .exile row 

 of three tells lini:fn). The lowest one, whiih is larger ihan Ihe tiLJuT 

 two, is Ihe murnis/'in'e. .-^itmelinus ihere .ire I'-uir df lliesr rtlls in llu- axile 

 row. This a-xile inw of three or iuur tells is lt)inied b>' the two suecessi\'e 



spi 



Fig. 356. 

 Macrosporangium of pine |,^.^p 

 (ovule), ^'h^, integument ; «, Lime 

 nucellus; ni, inacrospore; pc, 

 pollen chamber; pg, pollen 

 grain; an, axile row; spt, 

 spongy tissue. (After Fer- 

 guson.) 



