OF NATURE STUDY. —37 



absorb water. Where are these root-hairs most numerous ? Why are roots so 

 irregular, unlike stems? How would the soil affect the reg'ularity of a root? 



Each root has a root-cap at its tip, which is constant!}' renewed as it is worn 

 off by the soil, throuj^h which it forces its way. This root-cap is a very 

 important part of the root. 



Examine the roots of clover and other members of that family of plants 

 (bean, pea, etc.) You will find small enlarg-emonts called "nodules." These 

 nodules play a very important [lart in the nourishment of these plants, as they are 

 tenanted by minute forms of plant life (bacteria), which have the ]iowi'i- of 

 assimilating;- nitroi>^en liirectly from the air, wiiich [ilants and animals cannot 

 do. Thus the plants of the clover family are rich in nitrogen, and are valuable 

 fertilizers of the soil, as farmers have long known. A crop of clover ploughed 

 under is the ver\' best |)re[>aration for a cro[i of wheal. In dermany, tiiese 

 bacteria have been cullivatetl anil |)rei)ared for sale, jusi as phosphates are sold 

 as fertilizers. 



One of the best nature study exercises is to have each pupil plant a tUizen or 

 moi'e seeds of various kiiuls, (wheat, bean, pea, corn, melon,) anil report eaih 

 week or oltener u|)on their growth. The teacher should keep a few seeds of the 

 same kind growing for class demonstration, to correct errors and suggest new 

 work. 



TREKS THAT SHED Tlli;iU BARK. 



We ai-e all familiar with the iihenomenon of trees shedding their leaves. We 

 know, too, that in spring tlu'\- slu'il the scales which enclosed the Iniils all winter. 

 Later they shed most of the parts of the flower, the calyx, the corolla, and the 

 stamens. Then, usually, at the close of the season, the fruit falls. There are 

 exceptions to nearly all these statements, but generally speaking they aie true. 



Most of our trees shed their bark also. This is most evitlent on the s\camores 

 and birches, hut it is none the less true of otliei- trees. In winter the branciies of 

 the svcainore glistrn along the river vallejs, <'ind the hiteness of the leaves in 

 spring marks these trees distinctly against the sui'iounding greenness.. This 

 process of shedding the bark is quite evident in tlie while pine, from which the 

 bark scales in rather regular four-sided patciies. The shag-bark hickory sheds 

 its bark in striivs, which gives the name to the tree, while the rough surfaces ot 

 the maple, oak, walnut, and other trees shows that the same process is going on 

 there though less regulaily. It is, in fact, a necessity of their mode of growth. 



Thegrowtii of our common trees takes place in the area just under the bark, or 

 between the bark and the wood. This area is called the cambium. It grows both 

 inwards and outwards, forming wood on the inside and bark on the outside. As 

 the tri;e increases in circumference, the hark of jirevious years' growth is sho\'ed 

 outward, but being too small to cover the increased circumference it splits more 

 or less irregularly, and eventually scales off verj' quickly and completely in the 

 sycamore, and more slowly in the maple and other trees. 



Some trees, e. g. , palm, and some plants, e. g. , corn, lih', do not grow as 

 above described, and in these there is no t:)ark, although the outer layers of cells 

 are somewhat different from the inner ones. These trees and plants have points 

 of growth throughout the stem, and the wood is formed at these points in bundles. 



In the more adviinced classes the pupils should observe the relation between 



