ANNUAL RINGS OF GROWTH IN CARBONIFEROUS WOOD 
WINIFRED GOLDRING 
(WITH PLATE XIV) 
_ In a discussion of anatomical structure and climatic evolution, 
JErFRey' emphasizes the absence of annual rings in Cordaitean 
wood from the Carboniferous in latitudes south of England as 
indicative of uniformity of climate, in contrast with the conditions 
in the Triassic period, in which coniferous wood with annual rings 
is found as far south as Arizona. His statement is as follows: 
n the Paleozoic trunks which are supplied by the geological formations 
of Southern Canada the organization of the wood shows great uniformity, and 
there are no modifications of structure which indicate any periodicity in annual 
conditions of growth. The truth of this statement is well illustrated by - 
wood of a Cordaitean form from the Permo-Carboniferous of Hampton, Pines 
frequently found in regions of higher latitude... . . The next illustration 
shows the organization of a Carboniferous Cordaitean wood (Mesoxylon) from 
the northern part of England, and consequently of considerably higher latitude 
(54° N. in contrast to the 46° N., the latitute of Prince Edward Island). The 
annual rings in the wood from the English Carboniferous are clearly marked. 
For comparison with the situation revealed by the Cordaitean wood from 
Northern England, a trunk from the Triassic of the southwest region of the 
United States (Arizona) isshown ..... The annual rings are not so distinct 
in the photomicrograph as they appear on the weathered end of the actual 
petrified specimen. It will be clear from the information supplied in this case 
that as far south as Arizona in the Triassic annual rings were more or less 
clearly marked. A noteworthy variation in the annual temperature in that 
somewhat remote epoch is thus indicated.2_ This situation presents an inter- 
esting contrast to the climatic conditions which prevailed in the region of 
Prince Edward Island toward the end of the Paleozoic. If the situation be 
summarized, it is clear that in the later Paleozoic the difference between 46° N. 
and 54° N. means the presence in the higher latitude of annual rings and their 
absence in the lower one. On the other hand, in the beginning of the Mesozoic 
(the Triassic), even at a distance of 10° south of the latitude of Prince Edward 
Island, annual rings were quite clearly developed. 
* JerFrey, E. C., The anatomy of woody plants. 1917. 
? This might indicate variation in moisture instead of temperature. 
— Gazette, vol. 72] [326 
