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on the Genus Drimys . 
a considerable amount of material makes it clear to us that, so far as the 
root of D. color ata is concerned, the appearance of scalariform pitting is the 
usual result of injury in a smaller or larger number of the tracheides. 
Similar phenomena were found to hold for seedlings as well as the root of 
the adult. 
It is natural to compare the conditions resulting from injury in the 
stem of D. colorata with those found in the root. A much more limited 
amount of material was at our disposal in the case of this organ. A large 
number of sections have been prepared, however, both of the adult and 
seedling wounded stem. In no instance was there any indication of the 
fusions of pits such as are found quite generally in the lateral walls of the 
vessels of the vascular Magnoliaceae, as well as other dicotyledonous 
families ordinarily regarded as holding a higher systematic position. It 
seems natural to explain the difference of behaviour of these two organs in 
the case of injuries, so far as they may not be due to the limited amount of 
material of the injured stem, to the greater conservatism of the root. 
The significance of this statement will become apparent at a later 
stage. 
As a preliminary to the interpretation of the results of injury in 
the case of Drimys , it is necessary to devote some attention to the general 
features of organization of the vessel in the Magnoliaceae (including the 
Trochodendraceae) as a whole. The monotypic genus Liriodendron will 
serve to point the present remarks, although it is well to state that a large 
number of other genera have likewise been examined in the present 
connexion. Fig. 10, PI. VII, shows the organization of one of the vessels 
in the root of Liriodendron tidipifera. The vessel is flanked on either 
side by other elements of the wood, both fibrous and parenchymatous. 
The trachea or vessel is of most importance from the standpoint of the 
interpretation of the traumatic phenomena of Drimys . In the upper and 
lower regions of the wall may be seen rows of opposite pits, which are 
clearly bordered and serve to bring about lateral relations with an adjoining 
vessel. Starting from the middle of the vascular element and descending 
may be seen a region of actual perforation, affording an unimpeded com- 
munication with another below the plane of section. The apertures in this 
case are the result of the loss of borders and likewise the partial fusion of 
the pits, which characterize the lateral walls of the vessel. The correctness 
of this interpretation may be easily inferred from an inspection of the 
figure. For comparison with Fig. 10, PI. VII, another vessel from Lirio- 
dendron of somewhat different type is presented in Fig. 11, PI. VII. Here 
the lateral pits are for the most part elongated and belong to the type 
known as scalariform. In the region below the middle the vessel is per- 
forated in this instance, as in the other case, so that the openings have resulted 
from the lateral pits having lost their membranes as well as their borders. 
