390 



GENERAL MORPHOLOGY OF PLANTS. 



presence of the " bordered pits " in the wood cells which appear 

 like minute openings in a bordering circle, in one view, and 

 elliptical in edge view (fig. 356), the large pits being on either 

 side of a middle partition, each with a minute opening on the 

 outside. Resin ducts also occur in the wood. The fruit of the 

 conifers is mostly a cone fruit, the seeds being borne on the inner 

 face of scales which are united around an axis in the form of a 

 cone. In the ground hemlock or American yew, the fruit is a 

 berry with a red pulp, but here the pollen-bearing sporophylls 

 are arranged in the form of a cone called the staminate cone, 

 much as they are in all of the cone-bearing Gymnosperms. 



LIFE HISTORY OF THE PINE. 



543. The staminate cones and pollen. The staminate cones 

 are borne in clusters at the ends of branches occupying the posi- 

 tion of a whorl of branches. Each cone consists of a short axis 

 covered by short scale-like structures 

 compactly arranged in a spiral manner. 

 Each one of these scales is a modified 

 leaf, or sporophyll. Upon the under- 

 side are two sacs which open by a slit 

 at maturity and scatter the pollen. All 

 in a cone, or cluster of a cone, usually 

 open suddenly and simultaneously, 

 emitting a cloud of the pollen. The 

 pollen is so abundant that it some- 

 times falls as it were in " showers," 

 covering leaves, etc., with a thin, 

 yellow-looking powder, resembling 

 " flour of sulphur." The scales are called stamens, hence the 

 name staminate cone. The pollen grains, however, are developed, 

 four from each mother cell, precisely as the spores are developed 

 in the spore cases of the ferns, mosses and liverworts. The 

 pollen grains are, therefore, small spores (microstores] , the anther 

 sacs are small spore cases (micros porangia) and the stamens are 

 small spore-bearing leaves (microsporophylls) . The pollen grain 



Fig. 358. 



Spray of white pine, showing 

 cluster of male cones just before 

 the scattering of the pollen. 



