SPEBMAPHYTES : PH^NOGAMS. 131 



the outer bark becomes split and irregular, and portions die, 

 becoming brown and hard. 



The tree has a very perfect root system, but different from 

 that of any pteridophytes. The first root of the embryo per- 

 sists as the main or " tap " root of the full-grown tree, and 

 from it branch off the secondary roots, which in turn give rise 

 to others. 



The sporangia are borne on special scale-like leaves, and 

 arranged very much as in certain pteridophytes, notably the 

 club mosses ; but instead of large and small spores being pro- 

 duced near together, the two kinds are borne on special 

 branches, or even on distinct trees (e.g. red cedar). In the 

 Scotch pine the microspores are ripe about the end of May. 

 The leaves bearing them are aggregated in small cones ("flow- 

 ers"), crowded about the base of a growing shoot terminating 

 the branches (Fig. 77, A $). The individual leaves (sporo- 

 phylls) are nearly triangular in shape, and attached by the 

 smaller end. On the lower side of each are borne two spo- 

 rangia (pollen sacs) (<7, sp.) 9 opening by a longitudinal slit, and 

 filled with innumerable yellow microspores (pollen spores), 

 which fall out as a shower of yellow dust if the branch is 

 shaken. 



The macrosporangia (ovules) are borne on similar leaves, 

 known as carpels, and, like the pollen sacs, borne in pairs, but 

 on the upper side of the sporophyll instead of the lower. 

 The female flowers appear when the pollen is ripe. The leaves 

 of which they are composed are thicker than those of the male 

 flowers, and of a pinkish color. At the base on the upper side 

 are borne the two ovules (macrosporangia) (Fig. 77, E, o), and 

 running through the centre is a ridge that ends in a little spine 

 or point. 



The ovule-bearing leaf has on the back a scale with fringed 

 edge (Fj sc.), quite conspicuous when the flower is young, but 

 scarcely to be detected in the older cone. From the female 

 flower is developed the cone (Fig. 75, A), but the process is a 



