THE PLANT AND ITS PHYSICAL ENVIRONMENT. 



and where it produces seedlings in such quantity that they become a 

 veritable nuisance. This is in a deep scree-slope — the structure that is 

 often called a moraine by gardeners. This scree-slope was formed by 

 fiUing in a cutting into gravel over clay, some 4 feet deep, with stones, 

 granite chips, peat and soil. The seedhngs, as soon as they start growing, 

 send down long tap-roots, which, so far as I can judge, reach to some- 

 where near the bottom of the cutting. Natural water flows perennially 

 at the junction of the gravel and clay, and the plants, thus provided 

 for, never show any signs of wilting, nor are they ever watered during 

 periods of dry weather. Of course it is possible to grow Morisia 

 under conditions very different from these, but in such places I have 

 never seen it flourish as it does in the spot I have described, where the 

 plants are hard and stocky, with no sign of the lush weediness that 

 one often sees in this beautiful species. Other examples that might 

 be quoted in support of the power of colonizing particular localities 

 are the Spruce, Fir, and Scots Pine, where an examination of their 

 respective root systems at once gives the clue to the diverse habitats 

 wherein they severally thrive. 



The importance of attention to the relation of the plant to water 

 is seen in yet other connexions. 



One of the important results of grafting of fruit trees, &c., depends 

 on the interference with the normal water supply. Whilst grafting 

 renders propagation easy, it has other consequences also. Every 

 fruit-grower is aware of the importance of the stock, and he is also 

 probably aware of the effect of the influences making for deep coarse 

 rooting of apple and other fruit trees. Still it is amazing how much 

 ignorance still prevails. The formation of the dwarf spurs on which in 

 most apple and pear trees the fruit is chiefly or entirely borne results, 

 in a sense, from a reaction on the part of the plant to lack of water. 

 But the internal balance of water supply is a nicely adjusted one, as is 

 occasionally shown by the consequences of damage through accident 

 or ignorance to the leading shoots, resulting in potential spurs growing 

 on as wood buds when the leader, which, so to say, draws the water 

 past them, is cut back. Similar or analogous results of water starva- 

 tion are of course produced as the effects of root pruning, especially on 

 plants that have been over-luxuriant. On weaker plants root pruning, 

 as is well known, may either have no effect or else a prejudicial one. 

 [The production of characteristically large leaves on the stool shoots 

 of trees further illustrates the points under discussion.] 



Now the matter is not a simple question of the regulation of water 

 supply, for any interference with this important factor of plant growth 

 and development necessarily brings about a change in other conditions 

 within the plant. In the first place, along with the water, the nutritious 

 salts from the soil gain admission to the plant. No one knows better 

 than a gardener the effects of adding manures of various sorts to the 

 soil, so far as the obvious consequences to the plant are concerned. 

 But the horticulturist, like most other people, has the slightest of 

 knowledge as to what happens in the plant as the result of the addition 



