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vocal; and the tropical traveller, often surprized by these unearthly sounds of the 
forest, starts affrighted. The Wild Carrot contracts and inflects its umbels 
during rain, and unfurls them in dry weather: the air then sifts and filters 
through the interstices, thus ventilating the seeds that might otherwise decay 
from excess of moisture. The spiral valves of the Didymacarpus rexii are sensi¬ 
ble hygroscopes; they untwist in dry weather, and expose the seeds attached to 
the axis, to the genial and ripening influence of the atmosphere. In moist wea¬ 
ther, the valves will be found screwed closely together, completely impervious to 
air and moisture. Similar phenomena are very numerous, and examples might 
be indefinitely multiplied; but these are sufficient to illustrate my position. 
II. —Dietetics and Therapeutics, as applied to Vegetation. 
That roots are selecting, discriminating, and appropriating organs, there can 
be no reasonable doubt; nor can it be expected that all plants should subsist on 
the same kind of food. As plants are infinitely diversified in their appearance, 
condition, and the local circumstances under which they are found, with the phe¬ 
nomena presented in their secretions and excretions, it follows that a diversity of 
diet is necessary. Various earths, and diversified materials from animal and 
vegetable sources, afford the nutriment we commonly apply; but oftentimes no 
rule of discrimination is adopted, for the same unvarying routine is incessantly 
repeated. Some peculiar kinds of plants are so much out of the ordinary way, in 
their port and manner, that they must, prima facie , enforce the importance of 
discrimination being necessary. The Drosera rotundifolia , and even the Pin- 
guicula —the Dionaea mmcipula and Sarracenias —are all clearly more indebted 
to animal matter for their supplies than other sources, and hence are duly sup¬ 
plied with bristles, pouches, and traps, to entangle and to catch insects ; the 
decomposed animal matter being necessary to their well-being. 
In the year 1818, I discovered that the bulbs of Hyacinths, the Narcissus, 
Persian Iris, &c., grown in root-glasses, excreted carbonic acid gas, &c., by their 
fibres. Macaire has since verified the fact; though I remember that, when I 
communicated the circumstance to Mr. Edward Rudge, he expressed much scep¬ 
ticism regarding the fact. This has, however, lately attracted considerable notice, 
and is likely to command still greater attention. Gum anime is found in cakes, 
among the roots of the Hymencea courbaril; and it is notorious that the Sal- 
sola kali impregnates the soil, where it grows, with alkaline matter. The 
roots of many plants are very tenacious of life, and intense temperatures do not 
destroy their vitality; the roots of the Vitex Agnus castus will not be affected, 
though immersed in boiling water ; and boiling water may, in many instances, be 
applied to the roots of plants, without injury. Again, if a mass of roots be 
divided into two parcels, acetate of lead, in solution, being absorbed on one side, 
d 2 
