Some nature biographies; plant--insect--marine--mineral
John J. Ward
Paperback
(RareBooksClub.com, May 9, 2012)
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1908 Excerpt: ...these food materials, oxygen gas is given off as a waste product--waste so far as the plant is concerned. It will be seen, therefore, that while animals pollute the atmosphere by exhaling carbonic acid gas, plants, in the process of feeding, absorb and decompose this poisonous gas, retaining the carbon which it contains for their own use, and giving back its pure oxygen (which is of no use to the plant) to the atmosphere. Thus the animal supplies the carbon which is the chief food of the plant, and the plant in return affords the pure oxygen so needful to animal life. As previously remarked, a continuous water supply is necessary in the feeding process of the plant, and this is, of course, absorbed from the soil by the roots. From the roots it is passed through wood and pipe-like tissues up the stem to the leaves, and there the water-mains, so to speak, thin down and form a delicate network (popularly known as the veins or nervures), eventually becoming lost amongst the more simple cellular structure of the leaf. Here, then, we have the plant feeding on carbonic acid gas by means of its leaves, and drawing water from the soil through its roots. Although a leaf is generally but a very flat, thin structure, yet it is built up of several kinds of tissues. If we examine a section of a leaf under a microscope (Fig. 98), we find that above and below there is a surface skin or epidermal layer, and that between these layers two other kinds of tissues appear, amongst which the vascular strands or veins are embedded. The two epidermal layers in most leaves show a very different appearance; the upper layer is formed of rounded or, perhaps, brick-shaped cells placed closely together, and forming a strong protective covering to the more important tissues beneath. Fig. 9...