54 BOTANICAL GAZETTE [yuLy 
As an illustration of the difficulty in distinguishing these woods ) 
let us consider a fossil from California recently described by GOTHAN.® 
He identifies the specimen as follows. The fact that the resin canals 
are typically non-pine-like, with thick-walled epithelium, shuts out- 
Pinoxylon. The presence of wood-parenchyma and spirals in the 
spring wood shows its relation to Pseudotsuga. Pseudotsuga macro- 
carpa has ray tracheids with spirals, and in P. Douglasii they are 
absent. Thus the fossil, which he calls Piceoxylon Pseudotsugae, 
as it has no spirals in the ray tracheids, must be closely allied to the” 
Douglas fir, if not a fossil specimen of it. 
In the first place, as we have seen, Pseudotsuga Douglasii possesses | 
spiral thickenings in the ray tracheids. This, according to the 
author’s own line of reasoning, would exclude P. Douglasii. Further, 
let us consider the statements in regard to the presence of wood- -pat 
enchyma ‘and spiral thickenings in the spring wood. As has been 
shown above, both these conditions occur in Picea sitchensis, a spruce ( 
from the Pacific coast. Can we be sure whether this fossil is more 
closely allied to Pseudotsuga, Picea, or even Larix? As an added. 
reason for regarding the fossil allied to Pseudotsuga, the author states 
that the horizontal resin canals in the fusiform rays occur in an unsym- 
metrical manner. This same condition may be frequently observed 
in both Picea and Larix. One comes to the conclusion that the iden- 
tification of woods and fossils of Picea, Larix, and Pseudotsuga is an 
extremely difficult undertaking. 7 
SUMMARY 
1. Wood-parenchyma occurs on the outer surface of the summer 
wood of Picea. It is sporadic in its occurrence, and while usually 
appearing infrequently, may be strongly developed. 
2. Wood-parenchyma may be very sparsely developed in Lari 
and Pseudotsuga. : 
3- Septate tracheids occur associated with the wood- parenchyma - 
in these three genera, and show clearly the steps by which wood 
parenchyma has been developed from tracheids. : 
§ GoTHAN, Piceoxylon P ‘seudotsugae als fossiler Holz, Pseudotsuga sp. (aff. Do if 
lasii) als rezenter Baum; in H. PotontE, Abbildungen u. Deschertbonge Fo S 
Pflanzen, Lief 4. 1906. 
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