Foliar Ray in the Wood of the Dicotyledons. 655 



canals in Sequoia washingtoniana^ (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- 

 tanea 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, 

 Alnus 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 



