76 
Torrey.— Telephragmoxylon and the 
actual photograph a cross-section of Spruce wood and the position of wood 
parenchyma among the summer tracheides. In Picea , then, the midmost 
point of the differentiation of long tracheides into parenchyma has been 
reached. Yet logic requires us to suppose that the initial step in the process 
was the septation of the long tracheide into short tracheides, all of which 
were essentially similar. Such a situation appears not to have been detected 
in living woods, but in the fossil form under discussion just that condition is 
strikingly manifest. 
That it belongs to a different genetic series is of no consequence. We 
are here dealing with the origin of wood parenchyma, not with the origin of 
Picea , and we know that this element of the wood has originated several 
times and independently. 
It has been suggested that fully developed wood parenchyma at the 
end of the ring serves as a storehouse for foods which may be directly 
available to the developing cambium in the succeeding spring ; and that its 
differentiation was correlated with the progressive refrigeration which 
characterized the last part of the Mesozoic Period. 
Without bringing in a teleological explanation, we may believe that the 
original tracheide septation, as exemplified by the genus discussed in this 
article, constituted a superior mechanism for facilitating the rapid, radial 
transference of water and food-materials to the cambium at the same critical 
period of growth. 
It should be pointed out that a wood of this character has once before 
been discovered. In 1913 Miss Ruth Holden found, among the fragments of 
lignitic wood from the Jurassic deposits of Yorkshire, a specimen of Brachy- 
oxylon which, to quote her own words, is ‘ unique in the possession of large 
numbers of septate tracheides at the beginning (?) of each annual ring. The 
significance of these cells it is difficult to infer. Whether they represent 
incipient parenchyma or are related to an injury it is impossible to say, but 
the latter supposition is rendered improbable by their appearance in several 
successive years and the lack of any twist in the grain which would indicate 
proximity to a wound.’ 
Hence we are fairly certain that wood of the genus Telephragmoxylon 
was growing in Europe in the period which preceded the one in which our 
own specimens have been discovered. 
As to its taxonomic position, Telephragmoxylon is a member of the 
sub-tribe Brachyphylloideae of the tribe Araucarineae, family Pinaceae. 
Summary. 
Frotfi a study of living coniferous woods the theory has been advanced 
that wood parenchyma arose by septation of long tracheides, and that its 
first position was among the terminal cells of the summer wood. Pro- 
