I 4 6 PRACTICAL BOTANY 



a. A short stalk, or filament, which bears at its apex 



b. An expanded anther, with two swellings on the lower 

 surface (pollen-sacs, or microsporangia). 



II. Cut longitudinal sections of the male flower in which the 

 pollen is not yet ripe, and mount in glycerine : examine with a 

 low power. Note the arrangement of the parts as above 

 described : in the pollen-sacs note the pollen-grains in situ 

 (microspores). 



III. Mount ripe pollen-grains (i.e. such as may be collected 

 by shaking a male branch in June) in dilute glycerine, having 

 previously wetted them with alcohol. Observe 



1. The two large lateral -wings, usually filled with air, which 

 facilitate the transfer 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 the 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 morphological 

 equivalent. 



b. 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). 



