50 (iJ.IMI'SES IXTO I'LAXTLU'K 



(,)ii |)ullini;- it (Hit of the i^rouiul we see a bunch of 

 uhitisli tlircads or fibres spriny,"ing from the crown 

 of the |)laiit which is the junction between the 

 stem and the root;, and on these slender fibres are 

 hairs which are realh' the active part of the root, 

 for it is onl)' throUL,di these hairs that the rootlets 

 are able to absorb the licjuid from the soil, the 

 fibres simply actiny; as channels to c(jn\e)' the 

 watery nourishment to the stem and leaves. 



Common earth consists of small particles of 

 mineral substances such as flint, chalk, or iron, and 

 also of such vegetable matter as decayed leaves 

 and rotten wood. 



The spaces between the })articles are more or 

 less filled with air, each mineral particle being 

 enveloped with a film of water. However dry the 

 soil may appear, this will always be found to be 

 the case. It may be tested by weighing in an 

 agate balance some dry soil on a summer's clay. 

 'I'here is a ver\- delicate instrument called a 

 h\-groscope, which can tell us when there is the 

 slightest amount of moisture in the air, and a 

 clever German writer, V'on Sachs,' has termed this 



' Author of " N'egelahlu I'liysiology." 



