6 55 
Foliar Ray in the Wood of the Dicotyledons. 
canals in Sequoia washing to niana^ (Winsl.) Sud., it is to be inferred that the 
foliar ray has undergone a process of reduction in the alder under con- 
sideration. Furthermore, since similar conditions exist in other lower 
Dicotyledons which possess only uniseriate rays in the mature wood, the 
conclusion is reached that a considerable number of plants, although not 
in reality primitive, have reverted by the reduction of the foliar ray to 
a type of ray structure which characterized primitive Angiosperms. 
Vigorous Mature Roots. 
Fig. 6 illustrates a cross-section of a vigorous mature root of Cas- 
lanea dentata. Six more or less feebly developed large rays (x) radiate 
from the clusters of protoxylem. A similar condition is illustrated in 
Fig. 7, a cross-section of a vigorous root of Alnus yasha. In this root 
five much reduced aggregate rays (x) are seen to radiate from five clusters 
of protoxylem. In view of the phylogenetic importance of vigorous 
mature stems the persistence of large rays in vigorous mature roots is 
significant. 
The Node. 
In primitive plants which possess well-developed foliar rays these 
structures originate in the vicinity of the leaf-trace and gradually ‘build 
up ’ and enlarge in passing from the earliest formed wood of the node 
to that of the more mature portions of the plant. Fig. 5 illustrates a 
cross-section of the node of Alnus yasha. The foliar ray, which is strongly 
developed near the leaf-trace and in the first annual layer of growth, 
gradually disappears in the older wood. This reduction rather than 
compounding of ray tissue, which occurs also in Castanea , Castanopsis , 
Almis mollis , and A. acuminata , indicates, as do the vigorous ramifica- 
tions, that the foliar ray was once well developed in these plants and 
has gradually disappeared except from regions which are known to re- 
tain primitive characters. The retention of the foliar ray at the node is 
to be expected, since ancestral characters have been shown by Scott, 
Jeffrey, and others to persist in the vicinity of the leaf. The nodes of 
vigorous mature stems are, therefore, particularly favourable regions for the 
recapitulation of primitive features, and retain indications of the existence 
of foliar rays after they have disappeared from the rest of the stem. 
Traumatic Regions. 
Valuable evidence confirming the phylogenetic importance of the 
recapitulation of primitive characters in the regions just mentioned is 
afforded by a study of the traumatic reactions of the wood of these 
plants. It has been pointed out above that severe injuries, in wood which 
possesses well-developed foliar rays, produce a reversion to primitive 
stages of aggregation and fusion or to the uniseriate condition. From 
