Medullary Rays of Quercus. 985 
3. The fibro-tracheides forming the outer boundary of the ring are 
flattened and copiously pitted on their tangential walls. 
4. The outline of the ring is continued across the broad medullary 
rays, and usually dips inward in the ray. 
5. The cells of the uniseriate rays at the boundary of the ring are 
shortened, have their terminal (tangential) walls specially thickened, and 
contain more abundant coloured contents. Less clearly the same is often 
the case in the multiseriate rays. 
6. The parenchyma near the outer part of the ring contains more 
abundant coloured contents. 
7. When the tangential bands of parenchyma are multiseriate in the 
middle parts of the ring, they may be thinner and even uniseriate in the 
outer part. 
All or any of these distinctive features may be wholly or locally 
wanting. Yet by applying these tests I have found no species of Quercus 
devoid of annual rings, or at least of growth-rings which may or may not 
represent annual increments of growth. Abromeit (’ 84 ) fully appreciated 
the first three methods here enumerated of identifying rings, and by their 
means showed that in most evergreen types annual rings obscure to the 
naked eye are recognizable with the aid of the microscope. He stated that 
rings often cannot be detected in the cases of Q. dilatata, Q. lamellosa , and 
Q. chrysolepis. I find annual rings can be traced in the last two though the 
outline may be obscure locally; Q . dilatata I have not examined. 
A. Deciduous Types. Class I. 
Typical deciduous species differ in the exact structure of their pore- 
zone of wide vessels, as regards the tangential distance apart of the vessels 
and the number of concentric series of wide vessels present; but the 
latter feature varies with the environment in one and the same species. 
The manner in which the vessels outside this zone decrease in size also 
varies in different species, the transition being more or less gradual or sudden. 
The following Table briefly indicates the nature of the'pore-zone. The 
terms ‘ ordinary ’, ‘ moderate ‘ loose ‘ very loose * refer to the tangential 
distance apart of the vessels ; their tangential distance apart is measured 
(merely by inspection) in diameters of the vessels. The suffix ‘ seriate 5 
with the prefixed figures denotes the number of concentric layers of wide 
spring vessels, while the terms ‘ sudden ’ or 1 gradual 5 describe the mode 
of transition from these wide vessels to those outside them by decrease 
in size. 
These statistics show that even in deciduous species the pore-zone may 
be loose by reason of the tangential separation of the vessels. It may be 
added that in deciduous species, Q.rubra for instance, the first-formed vessel 
in the spring-zone may be smaller than some vessels immediately succeeding 
