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1913] HOLDEN—RAY TRACHEIDS 59 
Specimens of Taxodiwm distichum, wounded and normal, of 
Cryptomeria japonica, and Arthrotaxis selaginoides were examined, 
but in none were ray tracheids observed. 
CUPRESSINEAE 
Of the genus Chamaecyparis, PENHALLOW (6) has described ray 
tracheids in C. nootkatensis, and absent elsewhere. In this species 
they are quite common, usually constituting the entire ray when 
one or two cells high, continuing for a time as such, and then becom- 
ing transformed into a parenchymatous ray. Careful examina- 
tion, however, has revealed them in a number of other species. In 
C. Lawsoniana they are quite rare, but unquestionable. Fig. 7 
shows their characteristic shape, long and low, with very small 
bordered pits next the parenchyma cells, two such pits being 
shown in the figure. C. thyoides and C. plumosa both show after 
injury tracheids of the same general appearance as those of C. 
Lawsoniana. A number of specimens of C. pisifera were examined 
before any ray tracheids were found. In one badly injured branch, 
however, there was a marked reversion to the thick-walled type of 
ray cell characteristic of the Abietineae, and between rows of these 
cells was a row of squarish tracheidal ray cells. In C. obtusa they 
seem entirely absent, even after injury. 
In the closely allied genus Cupressus ray tracheids are much 
more common. Out of 7 species examined, they were present in 
5; while of the other 2 species, only a small amount of material 
was available for study. The most frequent mode of occurrence 
_ is as an entire ray one to three cells high, though they have often 
been observed on the margin of higher rays. In this genus the 
relation to wounding is often diagrammatic. C. guadalupensis, 
after wounding, showed large numbers of ray tracheids. Fig. 8 
shows a characteristic ray, but more commonly they constitute 
a ray one cell high, which soon turns into parenchyma; rarely they 
are marginal. C. Macnabiana presents the clearest case of trau- 
matic reaction. Here frequently numbers of tracheidal rays one 
cell high start out immediately after a wound callus, extend 
through one or two years’ growth, and then either die out or become 
transformed into parenchyma. C. goveniana showed the same 
