QYMNOSPERM^l. 



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. 281, B}. The daughter-cells 

 thus formed arc doubtless the homologues of 

 the pro thallium 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- 

 fine) is thin and 

 delicate (e and i, 



Fig. 281, B}. In Decalsae." 



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 



J-A male flower of r S P ik S <*> ?**). ^ *** 



baceata,- a, th poiien structurally similar to those de- 



Bacs. B, & stamen, seen from , " 



below, c, a piece of a foiiae- scribed above. The stamens are 



shoot, e, with a leaf, b, in whose .. , , , , . , . 



axil is a scaly jixis (the fe- short and broad, and each bears on 

 its back or outer surface two elon- 

 gated pollen sacs (Fig. 283). The 

 pollen grains are similar to those 



ovule; m, aril ; a;, a rudimentary Q Abies 



axillary ovule. (|3P~ By an error 



of the engraver the hair line from In TttXUS OaCCttta the male flower 



a; is carried about 1 mm. too high _..., ., _ . 



in the figure.) E, longitudinal differs from those described above 



section of an older ovule, but i J.T. t A i 



before fertilization ; i, integu- only in the shape of the stamens, 



which are peltate and lobed (Fig. 

 284, B). They bear attached to 



emen the Under SurfaCe three t0 



sfc*av l W8rA"B p llen - s " cs > which contain 



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, 



