42 



Gardening as a Science. 



Vol. VIII. 



source and origin of all nutriment ; that it 

 is prepared, first, in the ground, then passes 

 into, or is attracted by, that most recently 

 formed and porous termination of each fibre 

 of the root, which we are taught to style 

 spongiole or spongelet, and is conveyed 

 thence by some propelling power upwards, 

 to and through every organ of the plant, 

 which it thus supplies with appropriate food. 

 "Writing upon the sap of plants. Profes- 

 sor Henslow says: — 'The crude sap intro- 

 duced at the roots, consists of nearly pure 

 water, containing only a very small and va- 

 riable per centage of certain saline, earthy, 

 and gaseous matters in solution. It is a 

 very common opinion, and one upon which 

 most erroneous notions are sometimes built 

 by practical men — gardeners and others — 

 that this crude sap is directly employed in 

 the nourishment and development of the va- 

 rious parts of the plant. There is much 

 plausibility in such an assumption. Every 

 one acquainted with the practice of pruning, 

 is aware that, by cutting away some parts 

 of a plant, he contrives to throw the rising 

 sap into other parts; and he finds that in 

 consequence of such treatment, these latter 

 parts are better nourished, and become more 

 developed than they otherwise would have 

 been ; but in spite of so plausible an experi- 

 ment, the crude sap is not nutritious; we 

 might as well declare that we can receive 

 nourishment from a weak dose of Epsom 

 salts, or grow fat upon soda water. Living 

 bodies, whether vegetable or animal, can 

 only be nourished and developed by organic 

 matter. Now, crude sap may very possibly 

 not contain a single particle of organic mat- 

 ter. The mystery is explained by the fact 

 which physiological botany has ascertained, 

 that plants are endowed with the peculiar 

 faculty of preparing organic matter for them- 

 selves, out of the materials which the crude 

 sap contains.' 



" Crude sap is generally said to consist of 

 water, holding in solution a quantity of car- 

 bonic acid, derived from the decomposition 

 of decaying manure or vegetable matter in 

 the soil; but the notion is as crude and ill- 

 digested itself, as any thing can possibly be. 

 In fact, we know not what this sap is, or 

 how it can be collected. If we take either 

 the oozings of the vine, the subject best at 

 command, at early spring, when every re- 

 cently pruned shoot emits at certain recur- 

 rent periods of the day, drops of apparently 

 limpid water; or collect the sap of the birch 

 tree, by boring into its stem; we obtain sap, 

 doubtless, but always more or less blended 

 with the prepared juices of the stem and 

 bark. Assuming however, the droppings of 

 the vine as a type, we find a liquid almost 



insipid, but which — so far as our test of lime 

 water can determine — yields no trace of car- 

 bonic acid, but gives a very perceptible de- 

 position of lime, by adding a minute particle 

 of oxalic acid to the sap. This acid pos- 

 sesses an affinity for lime, so strong, that a 

 union with it takes place when the propor- 

 tions of each are very minute, and diffused 

 through a considerable volume of water. 



" Crude sap, therefore, if it ever be met 

 with pure, cannot be said to contain organ- 

 ized matter; but we may readily admit, that 

 any matter capable of solution in water ab- 

 sorbed by the root, will pass with it into 

 their vessels; and such soluble matters may 

 be common salt, nitre, potassa, or lime, — 

 also that peculiar compound of oxygen and 

 charcoal, which we call carbonic acid ; but 

 assuredly the most minute f>article of any 

 organized solid substance, even though its 

 bulk do not amount to the thousandth part 

 of a grain of dust, can never enter the 

 spongelets of the root. 



" To recur to Professor Henslow : — ' Not 

 one,' he says, 'of all the chemists whom the 

 world has yet seen, has been able to com- 

 bine the elements of inorganic matter, so as 

 to form out of them a single organic com- 

 pound. They can change one organic body 

 into another, as starch into sugar; but they 

 cannot make either starch or sugar directly 

 from the elements of which they consist. It 

 is to the vegetable kingdom alone that this 

 wonderful faculty belongs, and it is by the 

 leaves of plants that the operation is carried 

 on. The crude sap is merely instrumental 

 in supplying the leaves with the materials 

 necessary for the formation of organic mat- 

 ter; it is the proper juice created by the 

 leaves, and in which such variety of organic 

 matters are dissolved, which forms the real 

 nutritious fluid of the plant, as blood does 

 that of the animal. The importance of re- 

 taining all the leaves, whilst they are still 

 living, upon a plant, is sufficiently evident; 

 not one of them can be abstracted or injured, 

 without the plant being deprived of a cer- 

 tain amount of " power" for generating its 

 "proper juice." ' 



" Carbonic acid is emitted from the lungs 

 of breathing animals; and it is proved that, 

 under certain conditions, plants produce it 

 also. But have we any reason to suppose 

 that the roots absorb it from the soil? Phi-- 

 losophers assert the fact, but we question 

 the possibility of arriving at the proof. 



" The living principle — that vitality wliich 

 prevents decay, which repels the effort of 

 chemical agency, is the great mystery upon 

 which every phenomenon depends. We are 

 on this point utterly ignorant; all our re- 

 searches and most refined investigations 



