THE FERTILISATION OF FLOWERS. 



329 



in by this natural chevaux de frise, as in an eel-trap, we may find 

 inside an Arum a hundred or two small insects in durance vile. 

 Here, however, they find nourishment in the honey- secretion, and 

 here they, in due time, work out nature's will, in that they become 

 laden with the discharged pollen. So that when the opposing 

 hairs shrivel and wither away, the insect-crowd disperses itself, and 

 its units, undeterred by reminiscences of their imprisonment, entering 

 other Arums in which the stigmas have just ripened, duly cross-fertilise 

 the latter. 



Risks of fertilisation being omitted altogether are not lost 

 sight of in the economy of nature, and such contingencies are 

 often duly provided for in re- 

 markable ways. In Myosotis 

 versicolor (Fig. 229), for instance, 

 there is an evident intent to pre- 

 vent self-fertilisation, from the 

 fact that the pistil (si) projects 

 far above the stamens (a) in the 

 young flower (A), and is therefore 

 a likely object to be touched by 

 an insect which has come from 

 another " Forget-me-not," as this 

 flower is often named. But 

 such an arrangement, dependent 

 on insect visitation, might be rendered futile if no insect happened to 

 alight on the flower. In due time, however, the corolla is seen to 

 increase in length ; as it grows upwards, the stamens (a) are carried 

 upwards (B), until, in due time, they attain the level of the stigma (st), 

 and by discharging their pollen upon it will fertilise the pistil, if it 

 has not already undergone that process from a foreign source. Such 

 a contrivance appears tantamount to the declaration, on the part of 

 plant-nature, that, although cross-fertilisation is sought and preferred, 

 yet self-fertilisation is better than none. 



Besides the means just noted, there exist a large number of 

 expedients in flowers for securing fertilisation ; these latter contri- 

 vances relating to the form and shapes of flowers, to the special posi- 

 tions of its organs, and to adaptive details of flower structure. The 

 polity of a primrose, in the peculiar situation of its stamens and pistils, 

 as adapted to secure cross-fertilisation, falls under this latter division 

 of floral expedients ; and so, also, would all these peculiarities of sta- 

 mens whereby the discharge of pollen in a fashion adapted to avoid 

 self- fertilisation is secured. In some flowers (e.g. Parnassia), as the 

 five stamens ripen one after the other (before the pistil, as it happens), 

 each anther is laid back downwards, so to speak, on the stigma or top 

 of the pistil, so that the pollen escapes by the side farthest from the 



FiG. 229. MVOSOTIS IN ITS EARLY (A) AND 

 LATER STAGE (B). 



