86 



WILD LIFE IN CALIFORNIA 



Why this germ should be able to hold its ac- 

 tive power dormant for years, or why under 

 the influence of gentle heat and moisture it 

 awakens into life, biologists have, so far, been 

 unable to give us a satisfactory explanation. 

 But, as everybody knows, an almond placed 

 in the soil at the proper season will "sprout" 

 and in the due course of time the sprout will 

 become a tree which upon maturity will itself 

 produce almonds. 



The sprouting or germination of the seed 

 means that the cells of protoplasm have com- 

 menced to multiply, which, as heretofore 

 stated, signifies an increase of substance. For 

 the first few days the material for the growth 

 is supplied by the meaty parts of the seed or 

 nut enclosing the germ bud. The rapidly in- 

 creasing cells first form a shoot that takes a 

 downward direction into the earth and is the 

 beginning of the root system of the tree, and 

 another shoot is formed which grows upward, 

 which ultimately becomes the trunk of the 

 tree. Within a few days the first shoot has 

 sent out little rootlets and the upward shoot 

 has produced a couple or more of leaves. By 

 this time the supply of growing material 

 stored in the meaty parts of the nut has been 

 used up in forming so much of the infant 

 tree. However, it is a matter of indifference 

 to the youngster, for now being equipped with 

 leaves and roots it is independent of its 

 nursing bottle, for with the new appendages, 

 leaves and roots, it can draw from the air, 

 the earth and the moisture therein the ele- 

 ments it requires for its future growth and 

 existence. 



With all exogenous trees, of which the 

 almond is one, the most rapid increase or multi- 

 plication of cells, up to a certain limit, is on 

 the growing end of a shoot. At the same time 

 there is also a lateral increase of cells by 

 which the circumference of the shoot is en- 

 larged. 



The lateral growth by which the increase of 

 girth occurs is best exhibited in a cross section 

 of a tree trunk, which shows that with the 

 close of the first year the protoplasm vacated 

 the cells it had occupied after taking a rest 

 during the winter. With the appearance of 

 spring it moves outwardly and renews its work 

 of cell' building, which is continued until the 

 ensuing winter; this manner of proceeding 

 lasting during the life of the tree. The dor- 

 mant and active periods being plainly marked 

 by what are called the annular rings. A similar 

 action takes place in the formation of the 

 bark of the tree, only the protoplasm moves 

 inwardly in cell building. The vacated cells 

 in the trunk of the tree become a part of the 

 hardwood, while those of the bark constitute 

 the dry and dead-like parts. The soft and 

 outer part of the trunk, the sap wood, which 

 is cut off or eliminated in the sawing up of a 

 log for boards or timber is the part last occu- 

 pied by the protoplasm and is technically 

 called the cambium layer. 



By the continued addition of cells on the 

 growing end or tips of the stems and lateral 

 expansions of cells of the branches and trunk, 

 and similar extensions and expansions among 

 the roots, in the course of time, a tree is 



grown. As may be inferred from the fore- 

 going, this tree is composed of a multitude of 

 cells with thickened walls of cellulose. These 

 cells from the roots to the leaves are so con- 

 nected that in the growing season there is con- 

 stant circulation and interchange of materials. 

 Remarkable and puzzling as may be the force 

 that sends the solutions from the roots in the 

 earth, sometimes hundreds of feet up, to the 

 leaves that grace the top of the tree, even 

 more mysterious and wonderful is the conver- 

 sion by action in the leaves of the solutions 

 into the various forms resulting in chlorophyl, 

 protoplasm, cell walls, sugar, starch, resin, 

 etc., and the return to various parts of the 

 tree or plant of certain of the substances for 

 its growth or storage. 



Apparently from all accounts the most im- 

 portant and active agent operating in the 

 leaves is chlorophyl, the green substance that 

 gives the color to them. However, it is in- 

 operative without the action of sunlight on the 

 leaves. The surface of the leaves, especially 

 the underside of most kinds, is filled with 

 minute openings, so small that, except in a 

 few cases, a microscope is required to see 

 them. All of these openings to the inner part 

 of the leaf are guarded by a pair of lips or 

 valves, which open and close as the character 

 of the operations going on in the interior of 

 the leaf require. In the interior part of the 

 leaf, or that portion between the surfaces, 

 are numerous cells and air spaces, to which 

 the raw material gathered by the roots is 

 sent and distributed there by the leaf veins. 



The gaseous elements, such as carbonic 

 acid and the air with its oxygen and nitrogen, 

 are drawn into the leaf through the small 

 pores or openings mentioned. These elements 

 are important and the most extensive of the 

 contributions to the substances manufactured 

 by the leaf. The openings are also used at 

 times by the workshop in the leaf as vents 

 through which to discharge all excess of 

 oxygen or other gases that arise in the op- 

 erations carried on there. 



Asa Grey, the American botanist, in sum- 

 marizing his description of plant growth, 

 says: "The living parts of a tree, of the 

 exogenous kind, are only these: First, the 

 rootlets at one extremity; second, the buds 

 and leaves of the season at the other; and 

 third, a zone consisting of the newest wood 

 and newest bark, connecting the rootlets with 

 the buds and leaves, however widely sep- 

 arated they may be — in the tallest trees from 

 two to four hundred feet apart. And these 

 parts are all renewed every year. No wonder, 

 thrrefore. that trees may live so long, since 

 thfey annually reproduce everything that is 

 essential to their life and growth, and since 

 onb a very small part of their bulk is alive 

 at once." 



While the facts given have been fully estab- 

 lished, it must be said that all the mysteries 

 of the wonderful work shop in the plant or 

 tree leaf have not been revealed, especially 

 in relation to the activities and powers of the 

 chlorophyl. But as it is only within the last 

 seventy-five or one hundred years that the 

 history of the growth and life of vegetable 



