GYMNOSPEBM^. 



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 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- ^^%^\^Ao1^. 



tine) is thin and °l Ptnw syiwstru 



' showing the two pol- 



delicate (e and i, len eacs.. Magnified., 



_,, .^v T- — FromLeMaoutand 



Fig. 281, B). In Decaisiie. 



this case (as indeed is common) 

 there are two vesicular jjrotru- 

 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 

 Kg. 284.-^, male flower of "i" ^pikcs (Fig. 282). They are 

 Taxus baccata; a, th« pollen structurally similar to those de- 

 sacs. 5, a stamen, seen from •* 

 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, sic ; s, the scales. 

 Z), longitudinal section of the fe- 

 male nliwer in C more magnifled ; 



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 

 L!Thf3y"or""nScieSs"TJhi PoUen grains are similar to those 



ovule; m, aril ; !c. a rudimentary nf Ahi'p.<i 



axillary ovule. (^T By an error ^"'ca. 



of the engraver the hair line from In TaXUS laccata 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 • ji i p n 



before fertilization ; j, integu- Only m the Shape 01 the stamens, 



S,Tpe?mTdra™%ho"l^4''tSe which are peltate and lobed (Fig. 



S"t'^Jfv'n^e'(^±2'piaTn:'ri; ^^^, B). They bear attached to 



scailTa'v'lf"^','''rVai;;ienZy' the Under surfacc three to eight 



aril between the upper scale pollen-sacs, which Contain many 



leaves and the ovule. All the ^ ' . "^ 



figures magnified.— After Sachs, globose poUen grams. 



These examples will serve to illustrate the general struc- 

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



