THE LIFE-HISTOflY OP PLANTS. 



dS 



to form this protective shield. The active gi-owing 

 point, then, is just -within or above this shield, 

 protected by which the roots extend, while as growth 

 goes on, numerous root-hairs, as before explained, 

 issue from the sides of the roots and constitute the 

 most important agents of absorption. 



The essential office of a root is to take up from 

 the soU, or air, or water in which it is growino- suffi- 

 cient liquid to supply the requirements of the plant, 

 to effect the necessary solution of inert or insoluble 



all this marvellous activity and sensibility to impres- 

 sions is manifested by the protoplasm of the ceUs, to 

 which reference was made in the last section. 



The explanation of the necessity for careful ground 

 operations, such as trenching, digging, hoeing, stir- 

 ring, for appropriate potting-soils, and the like, is 

 surely afforded by the wonderful life-history of the 

 root-fibrils. 



Boot-action Supposing all the conditions 



favourable— the soil neither unduly loose nor un- 

 duly compact, its temperature neither too high nor 

 too low, its texture permeated with air, moist but not 

 sodden — root-action at once begins. The general 

 conditions, in a word, are much the same as those 



• Pig. 40.— Simple Fibrous Boots : Duckweed. 



Pig. 41. — Section througli a Boot, showiiig the tip, o, covered 

 by the root-cap, s j above are seen, on either side, the 

 root-hairs. 



matter, and provide for the loss occasioned by evapo- 

 ration. How it does aU this we shall shortly con- 

 sider. It is only necessary to recall the fact that, 

 though this is the essential wort of the root, other 

 duties are performed by it, such as the storage of 

 food before referred to, and the fixation of the plant 

 in the soiL How the tiny root-fibres penetrate the 

 groimd, wriggle their way among and between the 

 particles of soil, round some obstacles and over others, 

 has been alluded to under the head of Germination 

 (Vol. I., p. 86), where also the marvellous sensitive- 

 ness of the tip of the root to various impressions has 

 been mentioned. Perhaps there is nothing more 

 wonderful in the whole of vegetable physiology than 

 these evidences of life, verging even upon intelli- 

 gence, in the fine thread-Kke tips of the ^oots.^ And 



which are necessary in the case of the germination 

 of the seedling plant. (See Vol. I., pp. 23, 24.) 



By growth near the tip beneath the sheltering 

 root-cap, the root-fibres axe thrust in between the 

 particles of soU, as it were, in search of moisture, 

 and having found it, the root-hairs aire produced in 

 abundance to make the most of it. Gardeners well 

 know and appreciate the dense cobwebby masses 

 which are produced on vine-roots in a properly- 

 made border, and which may, indeed, be seen in 

 most cases where the roots are in a moist food-sup- 

 plying medium, though there are some plants in 

 which these hairs are never produced. 



How the Roots Peed. — ^AU being ready, the 

 action commences. And now what happens ? Our 



