112 BOTANICAL GAZETTE [AUGUST 
but very few have ray tracheids. The albuminous cells are never in — 
line with the parenchyma cells of the ray, but always above or below 
them. Often they are in line with two or three degenerating cells on _ 
the wood side. These facts support the view of JEFFREY (2) that — 
the scarcity of ray tracheids in certain Abietineae, including Abies, a 
is the result of degenera- _ 
tion. The albuminous 
cells, elsewhere insepa- 
ray tracheids, persist, 
PAS a ae —- while the ray tracheids 
a themselves have disap- 
— peared. The latter are 
probably represented — 
by the degenerating cells 
mentioned. 
Another observation 
supporting this view is 
that of the occurrence 
of ray tracheids in the 
wounded root of Abies amabilis. Hitherto all observers have reported 
ray tracheids absent from the wood of this species. Yet in a piece 
of root wood which had been wounded several times, undoubted ray 
1G. 15.—P. resinosa: old stem; cambial”region 
showing albuminous cells in line with ray tracheids. 
this case their ancestral presence in the genus Abies. 
General considerations 
The character and relationships of the ray tracheid have bee? 
described in the various regions of the individual plant. As has bee? 
shown, it is in the young root that the proof of its origin from tracheaty 
tissue is most conclusive. Here transitions were observed from short 
tracheids extending between the rays to ray tracheids of all kinds. 
A significant feature, which has not yet been emphasized in connection 
with these transitional areas, is the occurrence of degenerating cells. 
One of these has been incidentally illustrated in fig. 5 at *. 
