16 BORTHWICK—ADVENTITIOUS ROOTS AND RELATION 
tions through several year-rings of the wood until they ultimately 
merged into normal medullary rays, from which, as subsequent 
investigation proved, they took their origin ; and although differ- 
ing in some minor details, the adventitious roots in the different 
species to be described in this paper agree in one important 
point, that is, they all originate from medullary rays, which, by a 
process of cell-division, have become abnormally broad, so that 
they appear like cylinders running through the wood and phloem, 
whence by a process of apical growth they are continued out as 
root-rudiments into the cortex, through which these ultimately 
force their way to the exterior. Their increase, especially in the 
tangential direction, causes the elements of the xylem and phloem 
to assume a bent and twisted or wavy course, such as is found in 
the so-called Curled or Bird’s-eye Maple. 
A search through the literature indicated that the subject 
would repay further investigation, hence a detailed examination 
of each specimen was undertaken. My results, so far as they 
have gone, are in entire accordance with, and confirm those of, 
previous authors, but they will be allowed to speak for themselves. 
Before proceeding, however, to the detailed description of the 
species examined, a brief resumé of some of the more recent 
literature on the subject is given. I may mention that it has 
en my special endeavour to confirm the statements made in 
this paper by means of photographs. 
According to Strasburger!, Curled or Bird’s-eye Maple owes 
its origin to “the unusually sinuous course taken by the elements 
of the wood,” which he attributes to the production of numerous 
adventitious buds, and also to the formation of abnormally broad 
medullary rays round which the wood elements are forced to 
bend, and thus to deviate from their usual course. No mention 
is made of these rays being rhizogenous. 
Frank? points out that bird’s-eye formation in wood is not 
due to adventitious buds alone.- He finds that medullary rays 
may become round and enlarged, thus displacing the elements of 
the xylem and phloem, so that they must assume the character- 
istic wavy irregular course seen in this kind of wood. He further 
states that recent authors are fairly unanimous in the view that 
*Strasburger, Text-book of Botany, 2nd Eng. Ed., 1903, p 
oe Die Krankheiten der Pflanzen, 2nd Ed., Vol. I ( Pay p. 81. 
