190 



CASSELL'S POPULAR GARDEXING. 



have seen, extremely varied. An almost equal 

 amount of variation is seen in the arrangements 

 which prevent the access of undesirable insects, or 

 protect the flower from wet or other accidents. Xot 

 only is the flower often so constructed that it permits 

 and even favoui-s the access of some insects, but it 

 absolutely prevents the ingress of others. 



This exclusion is brought about in a variety of 

 ways, which our space will not allow us to dilate 

 upon. As illustrations, may be mentioned the sticky 

 hairs to entrap and stop the progress of ths unlucky 

 insect that alights on a flower or 

 a flower -stalk so guarded — e.g.^ 

 Azalea viscosa — the recurved bris- 

 tles, the overhanging cornices, like 

 so many rat-traps, that bar the pro- 

 gress of slugs and snails, of thrips 

 and aphides, the distasteful flavours 

 and odours which repel others. 

 Those who wish to follow out 

 these details are recommended to 

 consult Miiller's " Fertilisation of 

 Flowers," and Kerner's "Flowers 

 and their Unbidden Guests." Here 

 we must content ourselves by in- 

 dicating a few of the marvels of 

 plant history, and which, as we 

 have seen, are not only matters for 

 the pure man of science, or most 

 lascinating subjects for the obser- 

 vation of the amateur, but of such 

 direct practical importance that no 

 one concerned in the raising of 

 seedlings, or the production of new 

 varieties, can afford to nesiectthem. 



Inheritance and Adapta- 

 tion, — In taking a general review 

 of the subject it maybe said that the 

 varied forms of flowers and the diverse arrangements 

 of their parts are partly hereditary endowments, 

 partly the result of adaptation to surrounding con- 

 ditions and requirements. Pre-existent flowers, of 

 course, were adapted in the same way as those now 

 existing, but it is necessary to bear in mind that a 

 particular form of flower and a certain arrangement 

 cf parts may be perpetuated by hereditary descent 

 to some extent, independently of present adaptive 

 needs. Thus, a flower whose construction is adapted, 

 say, to the visit of a tropical humming bird, may 

 yet retain its form in our gardens, though it may 

 there be fertilised by thrip, aphis, or even slug ! 

 Flowers and other parts of plants often retain 

 by inheritance forms no longer of use, but which 

 were adaptations to a former set of circumstances ; 

 thus, we meet with parts and contrivances which 



Fig. 82.— Pollen-grains, emitting Pol 

 len-tube (higlily magnified). 



appear and perhaps really are now of no practical 

 value. Ultimately such forms may be expected to 

 die out and be superseded by others more in accor- 

 dance with existing circumstances (indeed, we have 

 evidences of this in the rudimentary organs and 

 ill-developed parts we constantly meet with). These, 

 however, are slow processes, as reckoned by human 

 modes of computation, and do not greatly concern 

 us from a purely practical point of view. All that 

 we would insist on here is that the form, arrange- 

 ment, colour, fragrance, movements, and general 

 mechanism of the flower, are 

 primarily adaptations which secure 

 the formation and succession of 

 numerous and healthy seedlings, 

 on the one hand by securing the 

 dispersal of the pollen, and its safe 

 transport to the stigma, whether 

 of its own, or more commonly of 

 another plant ; or, on the other 

 hand, by preventing access of 

 marauding insects or by insuring 

 protection against wet, cold, or 

 other injm-ious agencies. But — 

 secondarily, they may be trans- 

 mitted by inheritance, long after 

 the necessity for their occurrence 

 has passed away; and thus it is 

 that the gardener daily perpetuates 

 and by repeated selection actually 

 brings abcAit an enhanced degree 

 of those changes which were at 

 first purely adaptive, but which 

 have now lost their significance. 

 In such cases the gardener practi- 

 cally determines the form which a 

 flower shall take — according to Ii is 

 requirements and inclination, and 

 moulds it as it would naturally be 

 moulded by the conditions.- under which it lives. Of 

 course, there are boimds and limits to the gardener's 

 power, he is but an agent— often a very blimdering 

 one. The facts of which we have given so bald an 

 outline, and these indications of his power, should 

 surely intensify the interest with which he regards 

 the flower, and induce him still further to avail 

 himself of the opportunities that lie in his way. 



IMPREGNATION. 



The Formation of the New Plant.— In 



whatever way the pollen makes its way to the 

 stigma, once arrived there, if the conditions be 

 favourable, it begins to grow. The favourable con- 

 ditions, independently of a certain degree of tempera- 

 ture and moisture, are of course the perfect healthy 

 development of the parts concerned. In the case of 



