fiotvers of vegetables were supposed by I)r Darwin? 
to be necessary to the elaboration and perfection of 
their sexual organs, and to the production of fruit. 
Each petal of the corolla of a flower has, according 
to him, a vessel which conveys its juices to the extre- 
mity, where they undergo a change of colour, as is 
seen in some party-coloured poppies. From the ex- 
tremities of the petal, the juices are again returned,' 
as in the leaves, by other vessels, and employed for 
the sustenance of the stigma, anthers, &c. This of- 
fice of the petals may be inferred, he adds, from their 
vascular structure being visible to the eye ; from many 
plants putting forth their flowers in autumn, before 
any leaves appear ; and from others completing the 
process of impregnation early in spring, before their 
green foliage, or even their floral leaves, come for- 
ward ; lastly, from the white petals of the Christmas 
rose (helleborus niger) changing to a deep green af^ 
ter the seeds have grown to a certain size, and the 
nectaries, stamens and stigma have dropped off, facts 
which shew, that the .first structure was necessary to 
the production of the honey, wax, and pollen, but 
was no longer required after these were formed *. 
274. With respect to fruits, Dr Ingenhousz ob-< 
serves, that, whether they were ripe or unripe, whe- 
ther exposed in sunshine or placed in the shade^ 
they always vitiated the air in which they were confi- 
fted. His experiments were made on peaches, lemons, 
pears and apples, and the results were invariably the 
samef. M. de Saussure, however, found, that 
* Thysiologia, p 6 51. t Exper. V ol. i. p. 274. 
