O YMNOSPERM^E. 



397 



same figure.) In all cases, unless possibly the Gnetaceae fur- 

 nish some exceptions, the pollen grains become more than one- 

 celled before the formation of the pollen tube (Figs. 281-5- 

 6-7). When the pollen grains germinate i. e. , send out their 

 tubes they always swell up and 

 burst the cxtine (which slips off 

 in the Coniferae), and the intine 

 is then prolonged into a tube, 

 which is continuous with the 

 cavity of the grain, and into 

 which the protoplasmic con- 

 tents pass (Figs. 286 and 287). 

 The small cells take no active 

 part in the formation of the 

 tube, and from their similarity, 

 both iii structure and function, 

 to the small cells in the germi- 

 nating microspores of the Sel- 

 aginellce, there can be no doubt 

 that they are to be regarded 

 as constituting a rudimentary 

 prothallium. 



509. The female flower is 

 in most cases a similar elon- 

 gated axis, upon which are ar- 

 ranged spirally a considerable 

 number of phyllomes, each 

 bearing two or more naked ov- 

 ules. Thus in Abies pectinata 

 the female flower is the young Fig. SSS.-A, a bract, c, detached 



, . , . , f from the axis of a young cone of Abies 



cone, which consists 01 an axis --- - -- 



row 

 low 



pectinata, with the scale, *, bearing the 



988 71\ hparino- nar ovules, * (enlarged). if, upper part of 

 ^00, n) Dealing nar- a mature coue; sp, axis; c. bracts; , 



Iar 8 e 'y developed scales, bearing the 



8ee( i s on the upper surface (reduced). 



c i ri P e scale, with two winged seeds; 



^ ^ eed . wing (reduce l)._ After 



schacht. 



\ which in turn 

 /;, vt uu, u LII, 



fhir>V sr>fllps (<t <A rmnn 

 ICK SCaieS (S, S) upo . I 



their upper surface. The scales 

 are at first quite small (as in A), and it is only as the cone 

 becomes older that they grow larger. Each scale bears on 

 its inner face two inverted ovules (sk, Fig. 288, A). 



In Pinus sylvestris the structure is essentially the same as 



