254 PRACTICAL BOTANY 



air, which facilitate the carriage of the pollen by the 

 wind : these are extensions of the outer coat (extine). 



2. The central body of the pollen-grain, consisting 

 of 



a. A large cell, which constitutes the greater part 

 of the grain, and from which the pollen- tube springs. 



~b. A series of one or more smaller cells affixed 

 laterally to the wall of the pollen-grain at a point 

 between the wings : they are placed on the convex side 

 of the grain, which is not so completely covered by the 

 wings. These take no direct part in the formation of 

 the pollen-tube. 



B. Female branches or cones. Observe on a 

 Scotch Fir, towards the end of June, that there are cones 

 to be found in three different stages of development, the 

 position of which is constant. 



a. Small green cones, one or more of which occur 

 close to the apex of the shoot of the current year. Note 

 that the basal part, or stalk, bears brown membranous 

 scales, while the upper part is globular, and is marked 

 out into numerous square areas, which are^he apices of 

 the ovuliferous scales. 



Comparing a shoot, which bears such young cones, with an 

 ordinary vegetative shoot, it will be seen that the cones correspond 

 in position to the lateral buds, of which they are the morpho- 

 logical equivalent. 



I. Larger green succulent cones, which occur 

 laterally at the apical part of the shoot of the previous 

 year : the arrangement of parts on these corresponds 

 to that on (a). 



c. Cones larger than (ft), brown and with lignified 

 tissues : on these the scales are usually more or less 



