240 



BOTANY. 



453. The general structure of the reproductive organs 

 may be understood from a study of those of the pines. 



Fio. 141.— A cluster of stamlnate cones or flowers. A, of a Pine (Pmus 

 sylvestrisi, with a detached stamen. Natural size. B, showing the two 

 pollen-sacs. Considerably magnified. 



The pollen-bearing flowers — staminate flowers, as they are 

 generally called — are loose cones generally crowded into 

 considerable clusters. Each cone consists of a stem upon 

 which are many flattish stamens, each bearing two pollen- 

 sacs (Fig. 141). 



FtG. 142. — Pollen-cells (microspores) of Gymnosperms. A^ of a Cycad ; u, 

 rudimentary first stage (prothallium), one pollen-cell germinating. JB, 

 pollen-cells of a Pine, side and top views, showing bladder-like enlarge- 

 ments of outer cell-wall, bi; the rudimentary prothallium is shown here 

 also. Much magnified. 



