iqiq] 



BRIEFER ARTICLES 



439 



species of Amphilophiiim. Fig. 2 illustrates a cross-section of the stem 

 of one of these plants. There are 4 pairs of approximated multiseriate 

 rays in the fourth growth layer. The narrow segments of xylem be- 

 tween these wide rays are deeply depressed below the general outline of 

 the stem. They obviously are not correlated with a lobed or stellate 

 arrangement of the primary elements, but are due to differences in the 

 number of xylem elements formed by different arcs of the cambium 

 during the fourth growing season. 



That the deeply depressed segments which occur commonly in oak 

 stems, having 2-10 or more growth layers, are correlated with the 

 presence of pairs of approximated multiseriate rays rather than the 



Fig. I 



Fig. 2 



stellate arrangement of the primary elements, is indicated not only by a 

 comparative study of the stems of various arborescent dicotyledons, 

 but also by numerous facts in the anatomy of the genus Querciis. From 

 different species of oaks and from plants grown under different environ- 

 mental or experimental conditions, it is possible to secure a series of 

 stems showing various stages in the disintegration and disappearance of 

 multiseriate rays.'' The segments are most deeply depressed in specimens 

 in which the pairs of multiseriate rays are most conspicuously developed 

 (fig. 3). On the other hand, where the pairs of wide rays or their vestiges 

 ("aggregate rays, " etc.) are entirely absent, the stellate form of the early 

 cambium, which may be conspicuous during the first growing season or 

 two, quickly becomes circular, as in Castanea and Populus. Where there 



3 Bailey, I. \V., and Sinnott, E. W., Anatomical evidences of reduction in certain 

 of the Amentiferae. Box. Gaz. 58:36-60. 1914. 



