NATURAL SCIENCES OF PHILADELPHIA. 177 



cabinet of nature, and I have, therefore, to keep referring to it as the 

 means to still more important ends. 



Last year I had progressed only so far as to learn that foliage was governed 

 by this law. I have since been able to show that the production of the sexes 

 is governed in the same way. I can now show that the same law prevails in 

 determining the form of the parts of fructification. 



Larix Europica, as in these cones exhibited, has the bractea scarcely as long 

 as the scales, but I also exhibit other cones from the same tree in which 

 the bractea are double the length of the scales, and some of them inclined to 

 recurve in such manner that thej' much more nearly resemble the cones of 

 Larix Griffithii oi the Himalayas than they_do those of the species to which 

 they belong. In order more clearly to explain the law of their production, 

 I will go over again part of the ground I have before explored, in order to 

 make more clear the connection between past discoveries and the present 

 one. 



In the first year of infant life, vitality is not strong. The Larix is no ex- 

 ception. As a consequence of this light hold on life, the leaves are all en- 

 tirely free from cohesion with the main stem or axis. The next year life is 

 more powerful, — the axis thickens, and the leaves become mostly adherent, 

 having only the foliaceous awns free. The Larch, of all trees, devotes the 

 most of its strength to its main axis or stem. Year by year it accumulates 

 strength in it, until by ten or twelve years of age it will frequently be able to 

 make a growth of five or six feet in height of a single season. At this — the 

 height of its vigor — the reproductive age commences. 



The greatest stream of vitalitj' flowing through the main axis, the side 

 branches have a very weak development. In many cases the buds cannot 

 push forth into shoots at all, but in such cases that law which gives corres- 

 ponding strength to the leaves in proportion as it is abstracted from the axis, 

 causes the leaves — true leaves — to grow in tufts or verticils, on small woody 

 spurs. The axis in these spurs elongates every year ; by slitting them, the 

 annual gains of growth can be readil_y seen. Occasionally, bj' the accidental 

 breaking of the point of the branchlet along which these verticils are situ- 

 ated, or from some other cause, the stream of vitality along that line is checked, 

 it will flow again into these verticils or arrested axes, and though they may 

 have been in the condition of spurs for ten or twenty years, they will again 

 develop into branchlets, with adherent leaves, as in the regular course of 

 things. 



Coming now to the bearing age, we find along a branchlet of the preced- 

 ing year's growth, before the growing season commences, numerous buds 

 at irregular distances along its length. The stoutest of these buds branch 

 out into new branchlets ; the rest remain as spurs. None of these produce 

 flowers on this, the shoot of the preceding year ; but the next year a few of 

 the strongest again develop into branchlets, a few more into verticils of true 

 leaves on the spurs, more into female, and the balance into male flowers. All 

 these different grades of vigor, and the consequences of the various grades 

 are apparent in these specimens (exhibited). The highest grade, the devel- 

 opment of the axis with adnate leaves, — the next spurs with free leaves, — the 

 third with fruiting cones, — the fourth with a vitality so weak that, after the 

 production of the pollen, the flower and whole woody axis immediately dies 

 altogether. 



Let us now pass from the Larch to a law of vigor recognized by every 

 observer as common to all trees. If two branches push out together, and the 

 one happen to get a little the start of the other in vigor, the stream of vitality 

 in that will be continually getting wider and stronger; and just in proportion 

 will the other lose. The strong branch in time will often take all, absorbing 

 all the feeders into itself, leaving the other side stream dry. Thus the inside 

 branches of trees, deprived of light and air, get weaker ; and the more fortu- 

 nate ones thrive in proportion. In the Larch this is beautifully illustrated. 



1869.] 



