GTMJfOSPBRMM 



395 



tain cells. Each pollen grain is at first a single cell, but by 

 the time it escapes from the anther it is a several-celled body, 

 by the formation of partitions within its cav- 

 ity (q, y. Fig. 381, B). The daughter-cells 

 thus formed are doubtless the homologues of 

 the prothallium of the higher Pteridophytes. 

 Each mature grain has a double wall, of 

 which the outer one (the extine) is hard 

 and thick, while 

 the inner one {in- 

 tine) is thin and 

 delicate {e and i, 

 Fig. 281, B). In 

 this case (as indeed is common) 

 there are two vesicular protru- 

 sions of the extine {bl, Fig. 281, 

 B), which give the grain the ap- 

 pearance externally of being three- 

 celled. 



The male flowers of Pinus syl- 

 vestris are collected into catkins 

 or spikes (Fig. 383). They 



I. — A sta- 

 men from the flower 

 of Pinus Bylvesi/ris, 

 showing the two pol- 

 len sacs. Magnified. 

 — From Le Mao lit and 

 Becaisne. 



Kg. 284. —.4, male flower of 



ai'e 



Taxue b<uieata! a, the pollen structurally similar to those de- 



eacs. B, a stamen, seen from . -' 



scribed above. The stamens are 

 short and broad, and each bears on 

 its back or outer surface two elon- 

 gated pollen sacs (Fig. 283). The 

 pcjllen grains are similar to those 

 of Abies. 



In Taxus baccata the male flower 

 differs from those described above 

 only in the shape of the stamens, 

 which are peltate and lobed (Fig. 

 384, B). They bear attached to 

 the under surface three to eight 

 aril be'tweei/ the' upper pcaie pollen-sacs, which Contain many 



leaves and the ovule. All the ^ . •' 



figures magnified.— After Sachs, globose pollen grains. 



These examples will serve to illustrate the general struc- 

 ture of the male flower, which, with minor variations, 



below. C, a piece of a foliage- 

 shoot, s, with a leaf, b, in whose 

 axil is a scaly axis (the fe- 

 male flower), which is terminated 

 by an ovule, sk ; 9, the scales. 

 i>, longitudinal section of the fe- 

 male flower in C, more magnified ; 

 i, integument or coat of ovule ; 

 M, the body or " nucleus" of the 

 ovule ; m, aril ; tB^^rudimentary- 

 axillary ovule. (^^ By an error 

 of the t-ngraver the hair line from 

 X is carried about 1 mm. too high 

 in the figure.) B, longitudinal 

 seciion of an older ovule, but 

 before fertilization ; i, integu- 

 ment or coat of the ovule ; e, en- 

 dosperm (drawn showing the 

 cells) ; kk, the body or *' nucleus" 

 of the ovule (drawn plain, i. e., 

 not showing the cells) ; ss, upper 

 scale leaves ; m, rudimentary 



