On Descriptions of Vascular Structures 107 
fluids xylol is found to he rather too volatile to be easy of use, a 
mixture of equal parts of xylol and cedar-wood oil works, perhaps, 
most easily. If cedar-wood oil is used, the objects can very con¬ 
veniently he brought\up to this fluid by placing them in a 10% 
solution of cedar-oil in\bsolute alcohol, over calcium chloride in a 
dessicator. The spreading out of the drops of cecfar-wood oil on 
the slide should be accelerated by warming on the paraffin oven. 
The method is, of course, a much longer one than that of 
Harper and Fairchild, as the objects have to be brought up to a 
clearing fluid before they can be placed on the slicfe, hut it has the 
advantages of being easily applicable to both large and small 
objects and of involving no loss of material in the process of fixing 
to the slide. Moreover, the method can obviously he applied to 
material which has been fixed in any way. It is useful, among 
other purposes, in making slides of plankton material, and even 
with ready stained material which only requires mounting in balsam, 
I have found it convenient to mount on a thin layer of albumen ; 
by this means one avoids the shifting of the objects likely to be 
caused by the addition of balsam or of the cover-slip. 
ON DESCRIPTIONS OF VASCULAR STRUCTURES. 
J N describing the course of the vascular tissues in the stem, it is 
more convenient in some cases to trace them in the acropetal 
direction, in other cases in the reverse order. 
De Bary, 1 speaking of “common bundles” (/.<?. those belonging 
to stem and leaf), writes as follows. “ Their course in the stem is 
most clearly understood by following them from their point of exit 
in a basipetal direction, that is downwards. The description of 
their course in this direction also corresponds best to the facts, 
inasmuch as at least in most cases the development of the common 
bundles begins at the point of exit, and proceeds on the one hand 
towards the leaf, and on the other downwards in the stem.” For 
example one may speak of a leaf-trace as passing* through the 
cortex of the stem into the bundle-ring and then downwards through 
so many internodes before fusing with the leaf-trace of a certain 
1 De Bary : Comparative Anatomy, English Edition, p. 234. 
1 The metaphorical use of words signifying motion, in the same 
manner as they would be employed for describing the course of a 
road, avoids a lengthy periphrasis. 
