stronger if the pulsations are more rapid, so that the Doppler effect is introduced if the charge is moving. But with the model it is obvious that any such interpretation is unnecessary; for the important quantity is not the actual charge of the electron, but the volume of the ether in which there was a spreading of the net at such a time as to affect the point in question at the time in question.

SUMMARY.

Because of the apparently absolute nature of acceleration, as well as for other reasons, we find it necessary to assume the existence of the ether, and therefore desirable to learn as much as possible of its properties. To do this, we first reduce the laws of all its phenomena, including gravitation and the relativity-principle, to five equations, and then examine their meanings; and find that two of them are probably laws of the geometrical configurations of the different parts of the ether; two more, equations partially defining two convenient vectors, and stating the indestructibility of electricity; while the fifth, Hamilton's Principle, is a law of motion, expressing the perfectly efficient cooperation of the different parts of the fundamental mechanism of the universe.

From these laws we may draw certain conclusions about the structure and properties of the ether, which are not, however, enough to enable us to determine exactly what it is. But by a few simple assumptions, we obtain an imaginable model of its actions. And since the model is based directly on the electromagnetic laws, it may be applied, without fear of error, to any electromagnetic problem, to enable us to obtain a qualitative result without mathematical analysis.

Proceedings of the American Academy of Arts and Sciences.

VOL. XLVIII. No. 13. NOVEMBER, 1912.

CONTRIBUTIONS FROM THE PHANEROGAMIC LABORATORIES OF HARVARD UNIVERSITY. - Nos. 55-58.

THE HISTORY, COMPARATIVE ANATOMY AND
EVOLUTION OF THE ARAUCARIOXYLON

TYPE.

BY EDWARD C. JEFFREY.

CONTRIBUTIONS FROM THE PHANEROGAMIC LABORATORIES

OF HARVARD UNIVERSITY. NO. 55.

THE HISTORY, COMPARATIVE ANATOMY AND EVOLUTION OF THE ARAUCARIOXYLON TYPE.

BY EDWARD C. JEFFREY.

Received, September 28, 1912.

PART I.

FOSSIL woods of the Araucarioxylon type are extremely abundant in the Mesozoic deposits. The only living conifers with wood of this type are confined to the Eastern tropical region, to Australasia and to South America and are all included under the two genera Agathis and Araucaria. As a consequence of their habit, which differs from that of all living Conifers, except certain of the Podocarpineae, and of the organization of their woody tissues, the Araucarian Conifers have been most commonly referred to affinities with the Cordaitales, an important gymnospermous group of the Paleozoic. As will be shown in connection with the present investigations, the importance of these features of resemblance has apparently been much exaggerated. The association with the Cordaitales carries with it. the implication, that the Araucariineae are either the ancestors of the other existing coniferous tribes, as is quite commonly held, or else that they constitute a separate line of descent, distinct from the ancestral stock of the remaining Conifers, as has been maintained in recent years by Seward and Penhallow. It is obviously a matter of considerable importance to clear up the affinities of the Araucarian stock, not only from the standpoint of its particular origin; but on account of the light thus to be thrown on the vexed subject of evolutionary processes as a whole by reason of the abundant display of the group during so long a period of geological time. The present writer has devoted nearly ten years to the procuring of material of Araucarian Conifers living and extinct and to the developmental, experimental and comparative anatomical investigation of their various organs and tissues.