214 



CASSELL'S POPULAR GARDEXIKG. 



cooler place, and slightly bedewed with, a fine rose of 

 a water-pot or a sjTringe, when the table is cleared. 

 If any are only resting temporarily in their place, 

 without having the means of obtaining sufficient 

 moisture, these should be placed in water till again 

 required. With close attention to these and minor 

 details the flowers can be greatly economised for 

 future use when the demand too nearly approaches 

 the siipply. These remarks apply more forcibly to 

 the system, sometimes followed, of lajing the flowers 

 on the table-cloth, and working out designs thereon 

 with the same, in which case the flowers will quickly 

 suffer if not again placed in water. This custom of 

 laying the flowers on the cloth has not the slightest 

 good quality to recommend it ; all natural habit and 

 style of growth being, so to speak, lost. We have 

 not thought fit, therefore, to advocate this system in 

 any way, beyond stating that when such means are 

 employed it should only be to fill up a vacancy where 

 no suitable recexDtacle can possibly be placed conve- 

 niently ; but long shoots of trailing plants look very 

 pretty when allowed to rest on the cloth, in attenua- 

 tion, as it were, from either of the designs. 



Finally, om' remarks on dinner-table decorations 

 have all been made under the assumption that the 

 cloth was of the usual or ordinary colour. When 

 such is not the case, and coloured strips are laid 

 through the centre of the table, it requires more care- 

 ful judgment in the selection of both flowei^s and 

 foliage, to avoid any clashing between one and the 

 other. The colour of cloth most to be avoided is 

 green ; other shades do not so much matter; but in no 

 case do we think any shade surpasses a white damask 

 cloth in its entirety. 



THE LIFE -HISTORY OF PLANTS. 



By Dr. Maxwell T. Masters, F.R.S. 



WHAT TEE LEAVES DO— THE SAP. 



IN the animal kingdom the work of nutrition, 

 at any rate in all the higher groups, com- 

 prises several secondary processes, such as the 

 prehension of food, its mastication, solution, and 

 digestion. When at length, after a series of 

 changes, the food gets converted into blood, it is re- 

 quisite that the new or crude blood, together with 

 That vitiated and rendered impure in its transit 

 through the body, should be exposed to the atmo- 

 sphere or to the oxygen in it. This is effected, 

 in the higher animals and man, by its passage 

 through the lungs, where, by the agency of respi- 

 ration, the crude and impure fluid becomes oxy- 

 genated, and then, in the form of red arterial 

 blood, is pumped by the heart's action into every 

 part of the body. In plants the same general results 



are brought about in a simpler fashion, as might 

 have been anticipated, from their simpler structure, 

 and the terms circulation and respiration can only be 

 made use of in a general sense, and not as implying 

 exact identity of process. The roots and the leaves 

 may roughly be compared with the organs of pre- 

 hension of animals. The roots avail themselves of 

 the water in the soil, and, in addition, they exert a 

 solvent action, which enables them to render the inert 

 and insoluble matters suitable for the nutrition of 

 the plant. In this sense the roots seize and manufac- 

 ture what they require. The leaves have a similar 

 action. They lay hold of the gases in the atmo- 

 sphere, absorb them, and transmute them. Some- 

 times they absorb liquid or vapour ; under given 

 conditions they always exhale it. The result of the 

 conjoined action of the roots and of the leaves is the 

 formation of food — true food — fitted for the nourish- 

 ment of existing tissues and the creation of new ones. 



The *' Sap" and its Course. — Hence there 

 must be some communication between the roots 

 below and the leaves above. But — and this is a 

 point upon which the greatest stress must be laid — 

 that communication is indirect. There is in a plant 

 no continuous system of pipes or tubes, such as 

 exists in the case of the blood-vessels of animals. 

 The blood of an animal is of the same constitution 

 throughout, according to its twofold nature — that is 

 to say, that while the venous blood keeps its cha- 

 racter, the arterial blood is, in its turn, uniform in 

 composition, into whatever part of the body it may 

 flow. It is not so with the juices of plants. They 

 are not uniform in all parts of the plant, but they 

 have one composition in one place or at one time, 

 another in another situation or at a different period. 



It is necessary to insist upon these points, for the 

 old doctrine of the circulation of a crude ascending 

 sap, passing in regular channels and currents from 

 the roots to the leaves, and then down again in the 

 form of " elaborated " sap, is one to which gardeners 

 cling tenaciously, though the scientists, without any 

 exception, have long ago either greatly modified or 

 entirely abandoned it. Modern research has shown 

 that the facts observed by the gardener are suscep- 

 tible (even where the observation itself is accurate) 

 of a very different interpretation fi-om that which he 

 is accustomed to put upon them. 



We may here quote what we have said elsewhere 

 on this subject (Henfrey's " Elementary Course of 

 Botany," ed. 4, j). 564) : " In spring, when vegeta- 

 tion is most active, or at other times when special 

 circumstances favour growth in particular places, a 

 current of watery sap, containing relatively little of 

 the matters formed in consequence of leaf-action, is 

 specially manifest ; and as the ends of the shoots 



