REVIEW. 
87 
the general surface of the stem, leaf, or root, or by any peculiar portion of these organs? 
By whatever part or portion of the plant the food may enter, it must at any rate pass 
through the covering of the epidermis, which the earlier physiologists thought it could not 
do, but by means of pores more or less visible. Yet some of them described the epidermis 
as being of so close and compact a texture, that the eye, aided even by the best microscopes, 
was unable to discover in it the slightest vestige whether of pores or of apertures. But 
Hedwig and Decandolle detected what seemed to be superficial pores in the leaves at 
least of many plants, and so will any one else who will be at the trouble of repeating their 
observations with lenses of similar powers. 
" The next difficulty was with regard to the epidermis of the flower, fruit, and root. 
No pores had been detected in the flower and fruit, though it was evident that they were 
refreshed and invigorated by the access of moisture, and of atmospheric air ; and no pores 
had been detected in the root, though it was evident that the whole of the nourishment 
which the plant derives from the soil must of necessity pass through it. It was also evident 
that no aliment could be taken up by the plant, except in the state of a liquid, or of a gas, 
that is by absorption, or by inhalation, as the chyle is taken up into the animal lacteals, or 
the air into the cells of the lungs. The avidity with which plants absorb water was per- 
ceived and acknowledged even in the earliest times, and even by men who were not 
botanists. Anacreon, in one of his little trifles in honour of drinking, makes the very trees 
of the forest drink : — ' The black earth drinks, and the trees drink it,' that is, the moisture 
which it contains. 
" By merely immersing in water a plant of almost any species of moss that has been 
some time gathered, or long exposed to drought, so as to have had its leaves shrunk or 
shrivelled up, the moisture will immediately penetrate the plant, which will thereby resume 
its original verdure, an experiment establishing the fact of the entrance of moisture into the 
plant through the medium of the epidermis. 
" It might be doubted whether any of the moisture thus imbibed had passed through the 
root. But if the bulb of a hyacinth is placed over the mouth of a glass vessel filled with 
water so that the extremities only of the radical fibres shall be immersed, the water is 
imperceptibly exhausted, and the plant grows. The moisture must consequently have 
passed through the root. Plants seem indeed to have a peculiar facility in taking up water 
by the root from the infinite number of little absorbent bibulous sponges (spongioid) in 
which the fine fibres of the root terminate. This is the grand apparatus that nature has 
destined to the office of the absorption of vegetable nutriment, and it is owing to the power- 
ful absorbent property of the spongiolae of which it consists, that the scientific gardener in 
the transplanting of his young trees, or the scientific and ornamental planter, in the trans- 
planting of his trees of full growth, is so extremely careful to preserve even the minutest 
fibres and extremities of the roots. Sir Henry Stewart's Planter's Guide has taught him 
the great importance of these little organs. 
" Hales instituted a variety of experiments to show the absorbing power of the roots, and 
the force with which it acts. But as they were made chiefly on the sections of roots laid 
bare and immersed in water, they do not exhibit any direct illustration of the natural action 
of the spongioid, collecting nourishment at ten thousand different points from the moisture 
of the soil, and in this respect the experiments are defective. The next topic of inquiry 
was the absorbing power of the leaves, which Duharnel and Marriotte did much to elucidate. 
But the most satisfactory set of experiments upon the subject of leaves is that of M. Bonnet 
of Geneva, whose main object was to ascertain whether the absorbing power of a leaf was 
alike on both surfaces. With this view, he placed a number of leaves over water, so as that 
they floated on it, but were not immersed ; some with the upper surface, and others with 
