BOTANY 



287, 300) are similar in structure in all Coniferae. The sporophylls 

 are sometimes brightly colored, red or yellow, and may be peltate 



(Taxus), or scales with the 

 sporangia upon the lower 

 surface. The male flowers 

 are usually borne singly, but 

 may be in clusters (Pinus). 

 The number of pollen-sacs 

 upon each sporophyll 

 ranges from two (Pinus, 

 Abies, etc.) to a dozen or 



more in Araucaria. 

 an 



FIG. 302. Taxus baccata. Germination of the The development of the 

 pollen. (After BELAJEFK.) A, germinating po ii e n-sac is much like that of 

 pollen-spore, showing the division- into two ^ ngium in the L 



cells. B, second division, forming anthendial ,. , 



cell, an. C, an older stage, the antheridial Pdiales, and each sporogenous 

 cell, an, divided into two. (A, B, X375; cel1 S lves nse to a tetrad of 

 C, X 200.) spores. In the Pinaceae the 



outer membrane of the ripe 



pollen-spore is provided with two saclike outgrowths, or wings, which assist in 



the distribution of the spores by the wind. The outer cells of the wall of the 



ripe pollen-sac are sometimes provided with spiral thickenings like those in 



Equisetum. The pollen-sac opens by a longitudinal cleft (Fig. 300, I). 



The pollen-spore, when discharged from the sporangium, may be undivided 



(Taxus), but usually it has already divided into two cells (Fig. 300, D), of 



which the smaller one becomes the antheridium. The formation of the latter 



may be preceded by one 



or more divisions (Pinus, 



Larix) , the first-formed cell, 



or cells, being disorganized 



before the pollen-spore is 



ripe. 



Female Flower 



sp 



The ovule may arise 

 from the apex of a shoot 

 (Taxus), but usually it 

 is borne upon the upper 

 side of a scale. The 

 number in the latter 

 case varies from a single FIG. 303. Taxus bacca'M. A, section of shoot, ter- 

 one in Araucaria and minating in the young ovule, sp (X30). B, a 



Agathis, to many in slightly older one ' more enlar e ed ' snowing the 



> sporogenous tissue, sp. 



Cupressus. 



The ovules may arise directly from the sporophyll, as in Sequoia 

 (Fig. 305) and Cupressus ; or there is present a " seminiferous scale," 

 which is placed in the axil of the sporophyll. The nature of this 



