222 BOTANICAL GAZETTE [MARCH 
need only be noted in the present connection. In the center of 
text fig. 1 is the type of ray known as the aggregate ray (A, A’). 
This is a radial band composed of congeries of small or uniseriate 
rays and clusters of fibers. The leaf trace is represented in solid 
black at the interior of the segment. The aggregate ray originated 
probably in the clustering of uniseriate rays around the outgoing 
leaf trace, and seems to be the most ancient type of broad ray 
found in forest trees. It is found in the root and seedling stem of 
dy L/ e 
Sees 
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aay 
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Fics. 1, 2.—Fig. 1, synoptic diagram illustrating ray situation in Casuarina; 
fig. 2, diagram of birch root. 
Casuarina, and persists in the adult axis of C. torulosa. It is also 
characteristic of the adult stem wood of the alder and of the 
southern oaks. 
The second type of angiospermous ray, represented at the left 
of the diagram, is known as the compound ray. It is found in 
Casuarina Fraseri, in the mature axes of oaks of northern range, 
and in herbaceous Dicotyledons. Immediately outside of and 
subtending the leaf trace (black) is the aggregate condition already 
mentioned. Farther out toward the periphery of the stele, however, 
the fibrous parts of the ray have undergone a parenchymatous 
