W 
of Lathrea Squamaria, óc. 417 
mode of growth, that we must endeavour to find a solution of this 
problem. | 
By laws which almost universally prevail in the vegetable 
kingdom, plants imbibe moisture from the soil by means of 
their radical fibres, and gases and moisture from the atmosphere 
through the medium of pores in the cuticle of their leaves. 
These elements are conveyed into the parenchyma, where innu- 
merablé and inconceivably delicate organs, stimulated by light 
and heat, throw off the oxygen and retain the hydrogen and 
carbon. ‘These essential ingredients at once produce the green 
colour, and are converted, by a mysterious and hidden process, 
into the several substances of the vegetable body. Parasitical 
plants, in one or more respects, and in different ways, are excep- 
tions to these general laws. Though the Lathrea, unlike many - 
of its tribe, has leaves amply supplied with absorbents, these 
organs are doubly concealed in a cold subterranean laboratory, 
and there destined to breathe in darkness; while the flowering 
stem,—the only part in contact with the light,—is destitute of 
those cuticular pores through which air can be admitted, and by 
means of which the ordinary functions can be performed. The 
materials and the stimulus are at hand, but for want of the 
proper apparatus they cannot act. Again: the radicles of the 
Lathrea do not imbibe moisture immediately from the soil, but 
extract the already assimilated juices of its foster-parent; and 
whether we suppose these juices to be derived from the inner 
cortical layers after the accession of carbon through the leaves, 
or from the alburnum, where they are in a less combined state ; 
they probably contain no free hydrogen to minister to the gene- 
ration of the green colour. They may also undergo a further 
chemical change, either in consequence of the partial disease 
occasioned by the attack of the tubers, or in passing through the 
substance of the tuber itself. We know that in the dark, plants 
3H 2 invariably 
