10 TEMPLETON— EFFECT oF LATE Frost oN Woop oF ACER. 
the year—can be traced, but in no case is there any direct con- 
tinuation of the medullary rays through the two consecutive rings. 
Plate CXCII, Fig. 3 and Fig. 4 respectively, show the above 
rings in longitudinal radial section, and in these the same 
features are illustrated. It is specially evident from Fig. 4, that 
an unsuccessful attempt to form vasa was made early in the 
_ year, the result being the production at intervals of short columns 
of large parenchymatous cells, the transverse walls of which 
have not disappeared (a). Later in the year a further stage in 
the transition to vasa can be seen, for though the columns of 
cells are still short, the transverse walls have now disappeared 
(b). The transition from the parenchymatous cells to tracheides 
is clearly demonstrated in this figure. 
This abnormal behaviour ‘of the cambium appears to be the 
result of frost injury. In this connection it is interesting to 
note that, in the Records of the Scottish Meteorological Society 
for the year 1897,—the year in which the ring was laid down— 
frost was recorded in Edinburgh on consecutive days, from March 
30th to April 6th, and on the 1st of April the ground was covered 
with snow. 
Hartig* found a somewhat similar condition in the wood of 
several frosted conifers e.g. Pine, Spruce, etc. According to 
this author, the formation of an ice layer between the cortex and 
the young wood, results in the crushing and killing of the latter. 
The medullary rays extend through the ice zone undamaged, and 
when the ice melts they become extraordinarily broad, since they 
can expand without any counter pressure. On the inner side of 
the phloem, the cambium gives rise to parenchymatous tissue, and 
only eventually in the wood zone is normal wood formed. 
In the cases described by Hartig, normal spring wood of the 
year had been formed before the frost took effect, while in the 
tree under discussion, the cambial cells, though probably turgid, 
had. not undergone division. 
Hartig also. states that, in places, liable to frost, it is in he 
under stem portions of coniferous trees, i.e. up to 1-2 metres in 
height, that these frost rings may be looked for, and. it was just 
in that region of the Acer that the phenomenon could be 
_ observed. 
A transverse, cut, containing ph abnormal wood-ring, was set 
aside to dry, and on examination some weeks later, exhibited 
not only the usual fractures along the medullary rays (Pl. CXCI, 
Fig. 2a), but ale aye defined circular split (PI. CXC Fig. 2b 
and Fig. rb)..: 
-- Tensions are set. up i in CHS, ‘aeabee which, result i in splitting 
taking place along the lines of least resistance—usually ape 
, a 
* R. Hartig, Lehrbuch er tentren (1900), p. = see 
