994 Groom .— The Evolution of the Annual Ring and 
rays reaches a climax in Q. serrata , Thunb., which has high columns of ray 
tissue divided at moderate intervals by fibres ranged into bands which vary 
from thin biseriate lines to thick multiseriate frayed or solid masses. 
So far all the species whose rays have been described are deciduous. 
They all possess well-developed multiseriate rays, which, however, differ 
considerably in height and in degree of division (or aggregation). 
Series IV (Evergreen). 
In tracing out the series in evergreen species it is of interest to consider 
the extent to which distinctness of pore-zone and subdivision of the broad 
ray go side by side. The result of the inquiry is to demonstrate that in the 
first ten species as arranged in order in the second Table there is an un¬ 
mistakable correspondence between the structure of annual ring and 
medullary ray, and that only two suggestive exceptions occur. To render 
this clear, in the succeeding paragraphs the figures denoting the order 
of succession in the Table are given in brackets after the name of each 
species. 
As regards broad rays, the simplest occur in three species that are also 
in the first four in the Table, namely, Q. Emoryi , Torr. (1-4), Q . arizonica , 
Sarg. (1-4), and Q . hypoleuca , Engelm (1-4). The first of these (PL LXXVI, 
Fig. 19) has high true undivided rays, also high fusiform rays divided here 
and there solely at the ends by obliquely transverse fibres. Q . arizonica 
(Fig. 20) possesses plump true fusiform rays, as has Q. hypoleuca (Fig. 21), 
some of whose rays are traversed by infrequent transverse uniseriate lines 
of fibres. In Q. hypoleuca fusiform rays are superposed to form vertical 
series, the individual rays being separated by thick strands of fibres, also 
occasionally by a vessel. This species may show a few vertical fibres 
projecting into the ray from the margin. 
Q. dumosa (1-4), which is among the first four species according to 
structure of ring, is fourth as regards ray. The rays are smaller than in 
the three other species, fusiform, undivided or divided near the ends by 
oblique uniseriate lines of fibres. In addition, there are still smaller super¬ 
posed fusiform rays that show more extensive subdivision. 
Q. Engelmanni , Greene (7) (Fig. 22), possesses rays that are divided 
by transverse, oblique, and curling fibrous partitions. 
Q. chrysolepis , Liebm. (5) (Fig. 23), has rays about as thick as those 
of Q. Engelmanni , divided by obliquely transverse biseriate bands of fibres 
and penetrated by a few vertical marginal fibres. 
In Q. agrifolia (9) some of the rays (Fig. 24 a) are broader than 
those of the two species just described; these are divided by nearly 
transverse thick bands of fibres into shallow superposed segments (or 
rays). In addition there occur narrower rays (Fig. 24#) that are divided 
by transverse or oblique thinner ' strands of fibres, which become so 
