986 Groom .— The Evolution of the Annual Ring and 
on or near the same radius. Both these features foreshadow more marked 
ones in evergreen types. 
Pore-zone. 
Species. 
Density. 
Distance apart 
of vessels. 
Number of concentric 
series . 
Transition from wide 
to narrow vessels is :— 
Q. lob at a , Nee 
moderate 
O-I 
diam. 
4-seriate 
gradual 
Q. rubra, Linn. 
ordinary 
V] 
2 ~ l 
>> 
4-5-seriate 
moderate to sudden 
Q. obtusiloba, Michx. 
moderate 
J) 
2 (-4-) seriate 
sudden 
Q. coccinea , Wangenh. 
moderate 
O-I 
Cx-)2(—3-) seriate 
sudden 
Q. garryana, Dougl. 
moderate 
J_tI 
2 1 2 
„ 
1-4-seriate 
gradual 
Q. PrinuSj Linn. 
moderate 
0-2 
>> 
1-2-seriate 
sudden 
Q. macrocaipa, Michx. 
loose 
0-2 
(i-)2(-3-) seriate 
rather sudden 
Q. californica 
loose 
1-2 
1-3-seriate 
gradual 
( Q. Kelloggii , Newb. ?) 
Q. Macdonaldi , Greene 
very loose 
1-4 
J > 
multiseriate 
very gradual 
B. Evergreen Types. 
The annual rings of evergreen species show all transitions from the 
preceding (deciduous) type, to that in which the vessels near the inner and 
outer boundaries of the ring are smaller than those nearer the middle of 
the ring. Hereafter, I will refer to the annual ring as being composed 
of an * inner’, a ‘middle’, and an ‘outer’ zone, though the three zones 
are not sharply delimited. 
Class II. Sub-evergreen or Sub-deciduous. 
Some evergreen species of Quercus possess annual rings marked by 
a pore-zone and by a decrease in the calibre of the vessels in an outward 
direction until a minimum is attained in the outer zone of the ring. The 
main difference between such types of rings and those of typical deciduous 
species lies in the absolutely smaller calibre of the widest vessels. In this 
type of annual ring the limiting zone of flattened tracheides is well marked. 
The evergreen species of Quercus showing this structure of the annual ring 
approaching closely that of deciduous species also approach the latter in 
duration of their foliage, and hence may be termed sub-evergreen or sub- 
deciduous, for they shed all their foliage gradually during winter (Q. dumosa , 
Nutt), or throw off all their older leaves in spring either immediately before 
( Q . arizonica , Sarg.), together with ( Q . Emoryi, Torrey), or immediately 
after ( Q . hypoleuca , Engelm), the unfolding of the new leaves. 1 
In two of these species interesting deviations in the annual rings 
present themselves. Q. hypoleuca (PI. LXXIV, Fig. 1) in addition to its 
ordinary rings has others that are much narrower, are devoid of wide vessels, 
and show a maximum calibre of vessel in the middle zone. In Q. Emoryi 
(Fig. 2), a still narrower ring rather feebly delimited from its immediate 
1 For particulars concerning the defoliation I rely upon Sargent’s ‘ Manual of the Trees of 
North America’. 
