USES OF THE PARTS. 95 



formed. Hence, it is an axiom in vegetable physiology, that 

 the production of flower-buds depends upon the presence of 

 nutritive matter in sufficient abundance for their support. 



The use of the calyx and corolla is too uncertain and unim- 

 portant to demand much notice. The calyx is usually regarded 

 as a protecting organ, and the corolla as a part for the 

 embellishment of the sexes. They neither appear to be of 

 much- physiological importance ; more especially not the coroUa, 

 or it would not be absent in such large numbers of plants. 



The use of the stamens is to effect the fertilisation of the 

 young seed contained in the pistil. To this end, the pollen of 

 the anther must be applied to the stigma, the result of which 

 is, that an embryo, the rudiment of a future plant, is generated 

 in the inside of the young seed, and, when mature, is capable 

 of multiplying the species. It is, however, to be observed, that 

 the seed, when ripe, will not renew the species from which it is 

 derived, with all its individual peculiarities ; the seed of a Green 

 Gage Plum, for instance, will not, with any certainty, produce 

 a plant having the sweet green fruit of that variety, but it may 

 produce a 'Plum whose fruit is red and acid. All that the 

 seed will certainly do is to produce a new individual of the 

 Plum species : the peculiarities of individuals are perpetuated 

 by other means, and especially by leaf-buds. (See Book II.) 



It has been remarked that the freshness of flowers may he much 

 prolonged by any circumstance which hinders the act of fertilisation. 

 Orchidaceous plants in hothouses are an instance of this. In general, 

 from the absence of insects, or of those other disturbing causes to which 

 Orchidaceee are exposed in their native places, the poUen cannot come 

 into contact with the stigma, and so long as this is prevented the flowers 

 of many species wiU retain their freshness for weeks, as if in expecta- 

 tion of that event for which they were created. But as soon as the act 

 of fecundation is accomplished, that is to say, from twelve to twenty- 

 four hours after the poUen touches the stigma, the flowers coUapse, the 

 bright colours become dim, the ovary begins to enlarge, and the beauty 

 of the flower is gone. The same fact has been noticed in the Mght 

 Flowering Cereus, whose flowers will retain their beauty during the 

 day after blossoming, provided the stigma is removed. 



If the pistil of one species be fertilised by the pollen of 

 another species, which may take place in the same genus, or if 



