62 



tion. The anther is usually a double-celled pouch, the contents of which by 

 segmentation break up into a number of perfectly similar parts called 

 " pollen-grains," which though minute are complex in structure. When 

 these are mature the anther splits or dehisces (to open) and the pollen 

 escapes, but it needs in some way to be appUed to the termination of the 

 pistil, called the " stigma." When this application is effected, the pollen- 

 grain absorbs moisture, its interior portion swells, and actually throws out 

 a tube which often grows to a great length in making its way towards the 

 unimpregnated nucleus of the ovule, which is situated in the ovary at the 

 base of the pistil. In this nucleus a large cavity filled with protoplasm has 

 developed, called the " mother-cell," within which we find the embryonal 

 vesicle to which the contents of the pollen-grain is tiansferred by the 

 channel of the pollen-tube. This is fertilisation, and upon it depends the 

 production of seed, for the new individual plant has its beginnings from 

 this interfusion. 



Most flowers are hermaphrodite, or double-sexed — they contain both 

 the stamens (anther-bearers) and pistils within the same calyx or on the 

 same receptacle ; but there arc some species where the scxua) organs, male 

 and female, are found on different individual plants, so that some agency 

 for the transference of the fructifying pollen -grains is absolutely necessary, 

 or the species would soon die out. Many of the latter are anemophilous. 

 (wind-fertihsing plants), with inconspicuous flowers yielding no nectar, 

 therefore not attractive to insects. In these cases nature provides the male 

 blossoms with an abundance of pollen-grains, which are wafted by the wind 

 to considerable distances, and so are likely to reach female blossoms and 

 fulfil their all-needful function. 



MECHANISM OF FLOWERS. 



Darwin and others have proved that " cross-fertilisation is a most im- 

 portant factor in the continued vitahty of any species of plant, and gives 

 an enormous advantage in the struggle for existence where the conditions 

 of life are not wholly favourable." In the hermaphrodite or double-sex 

 flowers, where self-fertilisation is possible. Nature has provided in most 

 cases some wonderful contrivances to prevent it, and to insure cross-fertilisa- 

 tion by the transference of the all-potent pollen -grains from some other 

 plant of the same species. 



The adaptability of the hive-bee to the work of cross-fertilisation seems 

 most marvellcus, when we realise that in its separate expeditions in search 

 of nectar and pcUen it keeps to the flowers of the same species, otherwise 

 its visits would he of no service in most cases, and probably detrimental in 

 many. 



On the subject of hermaphrodite flowers, Cheshire says,- 



An examination of most blooms will show that the essential organs before 

 referred to (anthers and pistils) are so placed that an accidental or unaided 

 transfer of pollen to stigma is unlikely, and where this arrangement of parts 

 is not found it frequently occurs that the anthers ripen and dehisce much 



