SOME FEATURES IN THE ANATOMY OF THE MALVALES 
evolutionary tendencies in plants are found in Quercus, etc., by ana- 
tomical investigation and experiment. Studies of fossil ancestors of 
Quercus show that the uniseriate ray is primitive. A higher condition 
is seen where the rays are grouped in clusters to constitute the aggre- 
gate ray often found in relation to the leaf-trace. This condition is 
also present among others of the lower Cupuliferae, namely, Alnus, 
Carpinus, Corylus, and Betula. In this Angiospermous family, 
however, the conditions described are often found only in the first 
annual ring, or more persistently in the seedling, indicating that the 
aggregate ray is a relatively primitive condition, and consequently of 
phylogenetic importance (2). 
Another important anatomical feature is the distribution of wood 
parenchyma, in regard to which, a somewhat exhaustive investigation 
of many of the American species of the woody Dicotyledons has es- 
tablished, prehminarily, certain general conditions. The first is 
where the parenchyma is diffuse, that is, scattered throughout the 
woody portion of the stem; a second condition is vasicentric, and here 
the parenchyma is clustered around the vessels; the third mode is 
that where it is found only at the end of the annual ring, or terminal. 
That these respective conditions of distribution are of phylogenetic 
importance has been shown by investigation among the lower Angio- 
sperms. The Casuarinaceae, Fagaceae, Betulaceae, Juglandaceae, 
Rosaceae, etc., show diffuse parenchyma; while studies of the higher 
forms, i. e., the Oleaceae, Ulmaceae, Rhamnaceae, Parietales, Legu- 
minosae, Compositae, etc., show vasicentric parenchyma. From these 
examples it is evident that the diffuse condition is the more primitive, 
since it is so characteristic of the lower orders, and that vasicentric is 
more advanced, since it is similarly characteristic of the higher orders. 
As terminal parenchyma occurs both in the higher and the lower 
orders of the Dicotyledons, it is evident it is not on the same footing 
as the other two methods of parenchyma distribution, and investigation 
has shown this to be the case. Miss Holden (3) obtained the following 
results in her studies of the Salicales: Popiilus halsamifera L., nigra L., 
grandidentata Michx. and laurifolia Ledeb. possess normally terminal 
parenchyma, but in the traumatic and conservative regions, vasicentric 
parenchyma was found. Similar conditions appeared in Salix 
nigricans Smith, hookeriana Barratt, japonica Thunb. and daphnoidea 
Vill.; but studies of the root, young stem, and wounded material, re- 
vealed also vasicentric parenchyma. In summing up the conditions 
