1912] THOMPSON—RAY TRACHEIDS 337 
sisted sporadically in a few species, but in the majority have either 
degenerated or been transformed to parenchyma. 
Summary 
1. Ray tracheids, marginal, interspersed, and elongated, were 
observed in association with wounds in A. amabilis and A. 
concolor. 
2. They were also observed in uninjured material of A. homo- 
lepis and A. Veitchit. 
3. Their usual position was in contact with a series of degen- 
erated cells on one hand and a group of parenchyma on the other. 
4. Transitions from ray tracheids to parenchyma were common, 
some elements having both bordered and simple pits, and others 
pits with borders of various sizes. 
5. All the evidence points to ray tracheids being present in the 
ancestors of Abies and absent today by reduction. 
The writer is indebted to Professor C. $. SARGENT for permission 
to collect material in the Arnold Arboretum, and to Mr. R. B. 
THOMSON for material and advice. The work was carried on under 
appointment as an ‘‘1851 London Exhibition Science Research 
Scholar” of the University of Toronto. 
UNIVERSITY OF ToRONTO 
EXPLANATION OF PLATES XXIV AND XXV 
PLATE XXIV 
Fic. 1.—Abies amabilis: transverse section of wounded root, showing 
several series of traumatic resin canals; 
1G. 2.—The same: higher saeeae showing a row of traumatic 
resin canals; > 100. 
Fic. 3.—The same: radial section; X150 
IG. 4.—The same: radial section, showing marginal ray tracheid with 
bordered pits in section; 
IG. 5 bes same: fitete persed ray tracheid; X1 
Fic. 6.—Abies homolepis: radial section, ficdsating the presence of 
“ghostlike” decent! cell; X 400. 
