ELEMENTS OF STRUCTURAL BOTANY. 



gymnospermous, that is, naked-seeded. All the plants 

 previously examined, on the other hand, have their seeds 

 enclosed in ovaries ; hence they are all angiospermous. The 

 scales of the cone are to be regarded as open 

 carpellary leaves, and each of them, with its 

 pair of ovules, constitutes a fertile flower. 

 The pollen is carried by the wind directly to 

 Fig. 117. the micropyle of the ovule, there being no 

 intervening stigma; but, as the quantity of pollen produced 

 is immense, the chances of failure to reach the ovules 

 are very slight. At the time of pollination, the air in a 

 pine forest is full of pollen. The yellow scum often 

 found on water after a summer shower is chiefly Pine 

 pollen. After fertilization the ovules develope into seeds, 

 and the scales of the cone, which are origin- 

 ally of rather soft texture, attain a woody 

 consistency. This process of maturing, how- 

 ever, in the Pine takes considerable time. 

 The cones do not ripen until the autumn of Fig. us. 

 the second year, after flowering. At this time the scales 

 diverge from the axis, and the seeds are allowed to 

 escape, each of them being now furnished with a wing, 

 which enables the wind more readily to waft it away. 

 The number of cotyledons in the embryo is variable, 

 but is always more than two ; sometimes there 

 are as many as twelve. 



The wood of the Gymnosperms is essentially 

 like that of the Dicotyledons, and the stem 

 thickens in the same way. Certain differences 

 Fig. 119. w iH b e noticed in another place. 



Fig. 117. Single scale of Pine cone with its bract. (Wood and Steele.) 

 Fig. 118. Inner side of the scale, showing the two naked ovules. (Wood 

 Fig. 119. Stamin&te catkins of Ground Hemlock. [and Steele.) 



