THE FERTILISATION OF FLOWERS. 315 



precepts, we may readily enough find in its structure plain instruction 

 in the build of the flower. The circle of green leaves placed outside 

 the yellow blossom is, of course, the calyx. This greeri cup consists 

 of five leaves or sepals united in the primrose, but free and easily 

 separable in the buttercup or wallflower (Fig. 205, A, ca). The blossom 

 or corolla (Fig. 208, co) of the primrose exhibits similarly a united con- 

 dition of parts. We can tell that it consists of five petals, or leaves, 

 by counting its prominent lobes or projections. When we tear the 

 corolla in two, longwise, we readily perceive the five stamens (a), 

 which, however, in the primrose, exhibit a somewhat peculiar position, 

 in that, instead of arising from the end of the flower-stalk, like the 

 other organs of the flower, they spring from the sides of the united 

 petals (Fig. 208). If we seize the corolla of a primrose by its upper 

 portion, and pull it gently upwards, the entire blossom with its 

 attached stamens will become detached from the flower-stalk, 

 leaving the calyx and pistil on the latter organ. Then tearing or 

 cutting away the calyx, we may be favoured with a clear view of the 

 pistil itself, seated on the extremity of the flower-stalk. In the pistil 

 (Fig. 2 1 8) we behold a body consisting below of the swelled or rounded 

 structure already mentioned, and named the ovary (ov). This being 

 cut across, is seen to contain numerous seeds or ovules, as the case may 

 be, arranged around a central pillar named the placenta. From the 

 upper part of the ovary arises a long stalk, the style (st) of the pistil ; 

 and the style, in its turn, is capped by a flat head, the stigma (sg). 

 In the pistil of the primrose we therefore see the three typical parts, 

 already noted as constituting the central organ of the flower. The 

 pistil in this case, it may be remarked, consists of five carpels, so 

 closely united that it is only by the aid of the " law of symmetry " 

 (or that demonstrating the general correspondence of numbers in the 

 flower-parts) that we can determine its composition. Five is the 

 ruling number in the calyx, corolla, and stamens. Hence we con- 

 clude that the pistil of the primrose in its composition will conform 

 to the type of the other whorls of the flower. 



The physiology of the flower naturally follows the consideration 

 of its structure. Living action, in other words, forms the natural 

 corollary to living machinery or structure ; hence we may fitly 

 inquire into the manner in which the work of fertilisation is carried 

 on in the economy of the primrose. Leaving for after treatment, the 

 more special features of fertilisation, the general scope of the 

 function whereby, as we have seen, the immature " ovules " are 

 converted into " seeds " each capable of developing, when planted, 

 into a new primrose may be readily appreciated. The stamens, 

 each possessing as its essential part the anther or head (Figs. 216 

 and 217, a), develop the yellow dust, or pollen, as one of the two 

 elements concerned in the work of plant-development and repro- 



