PINE REPRODUCTIVE ORGANS 253 



development of the lateral axes. In autumn the male 

 inflorescences of the preceding summer can only be 

 distinguished from the purely vegetative axis by the 

 absence of the lateral foliage-shoots from the lower 

 parts of them. 



I. Separate a single male flower, and cut it longi- 

 tudinally in a median plane : it will be found to consist 

 of 



1 . An axis, which bears 



2. A number of staminal leaves. 



Detach some of these staminal leaves with a needle : 

 each consists of 



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). 



The pollen is ripe about the middle of June, and material 

 should be collected and preserved in alcohol at short intervals 

 during May and June, so as to illustrate various stages of 

 development. By cutting sections from such material, and treat- 

 ing as above directed, the history of development of the pollen 

 may be made out. 



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 



