96 



CASSELL'S POPXTLAil GARDENING. 



forefathers thought that roots had mouths, that 

 they opened them when there was a prospect of 

 a meal, and clpsed them when the supphes were 

 not forthcoming. Later on the supposed open 

 mouths gave place to equally supposititious sponges 

 at the tips of the roots, and even now gar- 

 deners talk freely ahout " spongioles," as if it were 

 quite certain that such organs existed and that they 

 sucked up the moisture from the soil just as a 

 sponge does. Even as an illustrative metaphor this 

 is utterly incorrect, for, unfortunately ior this 

 theory, it is now definitely ascertained that there are 

 no such organs, and that moisture is not absorbed 

 into the plant in the same way as water into a sponge. 

 We know now that the tip of the root is covered hy 

 an impenetrable root-cap of dead tissue, that there are 

 no openings whatever at or near the tip of the root, 

 at least none that are visible ; that therefore solid 

 matters, however fine, cannot be absorbed by the 

 root. What then is absorbed? The answer to this 

 question is — Water. 



Wliat th.e Boots Peed on.— Water.— It is a 

 prevalent error to suppose that the soil always 

 contains plant-food ready for immediate use. It 

 may do so sometimes and in small proportions, 

 but the general state of things is just the re- 

 verse. People have come to look on the soil 

 as a great soup-kettle, in which masses of solid 

 matter are plunged in nutritive juices, like pieces of 

 meat tir vegetable in a basin of broth, and they 

 imagine that all the roots have to do is just to suck 

 up the good things thus provided for them. The 

 soil does indeed contain earthy and saline ingre- 

 dients, as well as carbonaceous and other matters 

 suitable for plant-nutrition, but for the most part in 

 an insoluble or inert condition, so that they require 

 special modification before they can be turned to 

 account. 



Water, however, exists in all soils in more or less 

 abundance. It is more or less impregnated with air, 

 and contains a minute proportion of saline matter 

 in solution. As it is the primary requisite of the 

 plant, so it is absorbed with proportionate aVidity. 

 But if there are no open mouths, no pores, no spon- 

 fjioles, if the roots and root-hairs present to the 

 water an unbroken surface, it may be asked how the 

 water becomes transferred from the soil into the 

 root. That it does so id beyond question ; it is ap- 

 parent to every one, and every one acts on the belief. 

 Common experience places the matter beyond dis- 

 pute, and the demonstrations of the chemist, however 

 neatly and cleverly they may be devised, are in so far 

 superfluous. When it comes to the question how the 

 transfer is efieoted, then common observation fails to 

 supply an answer, and we must avail ourselves of the 



aid of the scientist. From him we learn by what 

 simple, yet none the less wondrous, means the matter 

 is accomplished. The water having an affinity, as 

 chemists say, for the ceU-membrane, wets it, soaks 

 its constituent particles, elbows them out of the way, 

 if the metaphor may be allowed, and so makes its 

 way through and between them tiU it gains the in- 

 terior of the cell, and there difEuses itself amid the 

 denser particles of the fluids within.. In other 

 words, the water passes from without to within the 

 cell by the operation of the process of " osmosis " 

 previously referred to. The circumstances that 

 regulate osmosis have been carefully studied by 

 physicists and chemists, but it is unnecessary to 

 refer to them here further than to say that the pro- 

 cess essentially depends on the varying physical 

 nature of the two fluids, on the nature and condi- 

 tion of the intervening membrane, the temperature, 

 and atmospheric pressure. 



By far the largest part of aU plants consists of 

 water. Juicy plants, like Lettuce, may contain as 

 much as 90 per cent., the hardest wood when fellei? 

 not less than 40 per cent. ( Warington.) Without 

 water the protoplasm could not fulfil its office, 

 without it the plant would be reduced to an inert 

 mass, with no more lite in it than in the drawers 

 and bottles in a druggist's shop with their varied 

 contents. The machinery would be there, the fuel 

 would be there, the raw material would be there, 

 but for want of the water the machinery would be 

 at rest, the fuel would be useless, the raw material 

 would remain raw. Water, then, is essential to 

 plants ; to secure an adequate supply of it is the 

 main office of the root, and it effects this by the pro- 

 cess of osmosis. The actual quantity of water taken 

 up is not necessarily an index of the amount' re- 

 quired, for plants may take up more than they 

 actually require, having the means, as we shall here- 

 after see, of disposing of the surplus. StiU, it is 

 " evident that the elimination of this surplus is so 

 much labour wasted. 



"Watering. — ^There is probably no one operation 

 of practical gardening that demands more discretion 

 in its performance, and gets less, than this matter of 

 watering. Plants vary extremely in the extent of 

 their requirements, according to their structure and 

 hereditary qualities. One wants a great deal, an- 

 other does with a scanty pittance. The same plant 

 at one season requires a thorough soaking, at an- 

 other period it is best kept without any. H the 

 temperature be high and the light intense, much may 

 be required ; if the opposite conditions prevail, the 

 supply of water must be curtailed in proportion. 

 The tendency of inexperienced gardeners and 

 amateurs is to water all plants in all seasons and 



