3 28 



FOURTH GROUP. SEED-PLANTS. 



In the Abietineae the well-known cones (Fir-cones, Pine-cones) are the female 

 flowers or fruits. The cone is a metamorphosed shoot with a large number of 

 crowded woody scales arranged spirally on its axis, and the ovules are formed on the 

 scales rarely singly, generally two and sometimes several together on each scale. In 

 the Abietineae in the narrower sense (Abies, Picea, Larix, Cedrus, Pinus] the semi- 

 niferous scales (squamae fructiferae) (Fig. 257 A, B, s) are apparently axillary structures 



in the axils of small leaves (<r), the scales of the 

 cone which grow from the axis ; but the observa- 

 tion of very young cones of Abies pectinata shows 

 that the seminiferous scale arises as a protuberance 

 on the base of the so-called bract-scale (the cone- 

 scale) and therefore is not axillary (see below). 

 While the latter subsequently grows very little or 

 not at all larger, this outgrowth from it increases 

 greatly in size and produces on its upper surface 

 the two ovules, w : hich adhere to it by one side 

 and turn their micropyles to the axis of the cone ; 

 the seminiferous scale of these genera must there- 

 fore be regarded as a placenta of large dimensions 

 growing out of a carpellary leaf (Fig. 257 c\ the 

 latter being naturally small or stunted in its 

 growth. The whole cone is therefore a single 

 flower with numerous small open carpels, usually 

 termed bract-scales, which are far outstripped in 

 growth by their seed-bearing placentas, the semi- 

 niferous scales. 



The development of the seminiferous scales 

 which are flat in Abies and Larix when the seeds 

 are ripe, and thickened at the apex in Pinus, has 

 been closely followed in Phms Pumilio (the dwarf 

 Pine) by Strasburger, who regards them as reduced 

 shoots. The cones which are intended to flower 

 in the next spring begin to form in the autumn 

 of the preceding year, and take the place of one 

 of the buds which are disposed in false whorls on 

 the summit of the shoots, and from which long 

 shoots are subsequently developed. A considerable 

 number of large scale-leaves are formed at the 



base of the shoot, and may still be seen on ripe cones. The seminiferous scales 

 appear in the axils of the bract-scales, and therefore some of the tissue of the vegeta- 

 tive apex of the axis of the cone contributes to their formation, though they are always 

 in connection with the bract-scales 1 ; they take the form of a flattened transverse 



FIG. 257. Abies pectinata. A a leaf detached 

 from the female flowering axis and seen from above, 

 J the seminiferous scale with the ovules sk ; magni- 

 fied. B upper part of the female flower (the cone) in 

 the mature state; sp axis of the cone (floral axis), 

 c its leaves (bract-scales), s the seminiferous scales 

 highly magnified. C a seminiferous scale J with the 

 two seeds sa and their wings./", reduced. 



1 The seminiferous scales cannot in this case be regarded as outgrowths of the bract-scales, 

 which is Eichler's view. But it is not clear why such a placental growth should not arise even 

 in the axil of the carpel (the bract-scale), without being necessarily therefore a metamorphosed 

 shoot. 



