164 BOTANICAL GAZETTE [MARCH 
once at the beginning of a season’s growth; a continuous row of 
cambial cells which have hitherto laid down chiefly fibers and tra- 
cheids, beginning with the first divisions of the year, form ray cells 
and only such thereafter. This is also the method in the stem of the 
mature plant. 
Among the living oaks there are exceptions, however, to the 
possession of rays of the type shown in figs. rand 2. Q. virginiana 
Mill. (Q. virens Ait.), the live oak, has large rays of a type in which 
the compounding has become nearly complete. This species is 
probably somewhat more primitive than the above-mentioned species. 
Fig. 8 shows a tangential section of a ray from near the pith in a large 
seedling of this plant. The structure of this ray very much resembles 
that of the fossil oak and of the black oak seedlings. In fig. 9 a 
portion of this ray is shown enlarged. The Japanese oaks have 
somewhat similar structure of the broad medullary rays, Q. Mirbeckii 
and Q. Sieboldii especially. In the shape of their leaves the oaks - 
of Japan show other probable signs of primitiveness; the general 
type is similar to that of the chestnuts. 
Not only does the large ray in its primitive condition occur in 
fossil and seedling oaks, and occasionally in mature plants of the 
genus, but it exists also in several genera of the lower Cupuliferae, 
namely in Corylus, Carpinus, Ostrya, Betula, Alnus, and perhaps 
others. The distribution of the large rays in the dicotyledons is at 
present being investigated in this laboratory by Mr. I. W. BAILEY. 
Figs. 11 and 12, transverse and tangential sections, respectively, of 
the wood of Alnus incana (L.) Moench., show in one of these genera 
this “false ray.” In this case the linear rays have become grouped 
together, but very little fusion has yet taken place. It would seem 
then that this fusion of rays, perhaps for the acquisition of greater 
storage capacity, which began in some primitive cupuliferous plants, 
and which is still maintained at an early stage in some of the living 
members thereof, has reached a culmination in the broad, solidly 
parenchymatous mass, the large ray, of many living oaks. 
That the “false ray” of Alnus and of other closely allied genera 
represents the primitive condition of the present large ray of Quercus 
seems undoubted, not only from its appearance in the lower Cupulif- 
erae, and in fossil and seedling oaks, but also from many other points 
