ANATOMY AND PHYLOGENETIC POSITION OF BETULACEAE 419 
different situation occurs. Casuarina Fraseri, for instance, shows 
in the primitive regions a ray quite Hke the type found throughout 
the wood of Casuarina torulosa. In maturity, the woody elements 
have been entirely lost and the small rays have become completely 
fused into an exceedingly large one. Such a ray is called compound. 
There is still another type, that found in Casuarina equisetifolia and 
Casuarina stricta. Here the rays in the first annual rings are in the 
aggregate stage. When the tree is old enough, a different condition 
from, that found in Casuarina Fraseri occurs. The rays do not fuse 
together to form one large ray. Instead, as the aggregate type passes 
into the outer rings of growth, there is a tendency to separate, or, in 
other words, to become diffused into small rays two or three cells in 
width. If a large section is examined, this diffusion will be seen to 
take place in a perfectly diagrammatic manner. Thus Casuarina is 
a generalized type, as appears when one looks at the matter from the 
standpoint of the ray formation. 
Turning from the Casuarinaceae let us consider the amentiferous 
forms in order to obtain some idea of the position which they occupy 
in the evolutionary scale. At present the Betulaceae and Fagaceae 
are placed in one cohort called the Fagales. This cohort is allocated 
by Engler eleventh from the base of the Dicotyledons. Since there 
is much uncertainty as to the exact relationship of these lower cohorts, 
the placing of the Fagales in the eleventh position simply means that 
the group belongs near the base of the Dicotyledons. Until recently 
the study of these forms, as in the case of the Casuarinaceae, has been 
confined largely to the reproductive organs. From such studies great 
diversity of opinion has arisen and no definite conclusions have been 
reached. In order that the reader may obtain some idea of the 
apparent confusion which has resulted, it seems desirable to give a 
brief account of the situation. 
The peculiar floral apparatus, the ament, has caused much un- 
certainty upon the part of observers. A large group hold that the 
floral structure is not a primitive but a reduced form. Van Tieghem 
(1868), as far back as 1868, after making a study of Juglans (belonging 
to the cohort Juglandales) and of the Coryleae, claimed that their 
floral anatomy was similar to that of the higher Angiosperms. Prantl 
(1887), in his study of the Cupuliferae, looked upon the Fagaceae and 
the Betulaceae as derived by reduction from plants with bisexual 
flowers, possessing a perianth, multilocular ovary, and suspended 
