( 245 ) 
so that branches of any size or even entire plants with their roots 
can be connected with the apparatus, or pieces of wood through which 
fluid must be driven downwards. By using long joining-pieces it is 
also possible to place the plant in a glass case or any other appa- 
ratus, which if necessary can be put up at a tolerable distance from 
the hydrosimeter, whilst the reading of the result on the latter 
remains possible. On the plate the apparatus is shown as it is used 
for the injection of the leaves of Rhododendron. 
2°. a lower tube with a glass tap (%); through this the mercury 
can be drawn off, the volume of which is to be determined. 
3°, a topmost tube, likewise with a glass tap &, which tube ends 
in a reservoir 4 filled with water. This is necessary to replace the 
mercury which is tapped through tube A. 
After this description of the apparatus shown in fig. A I wish to 
draw the attention to fig. B giving a representation of a metal 
clip, one attached to each of the three glass taps. The hydrosimeter 
is arranged for the use of one atmosphere as maximum pressure, 
this being at least for botanical investigations more than sufficient, 
whilst for the rest there are no obstacles to the use of a higher 
pressure, though it might make some further precautions necessary. 
But already with pressures of less than one atmosphere we meet 
with the drawback that not only do the taps leak, but that even 
the whole tap-stopper is pressed out. This is indeed not to be won- 
dered at, considering the stopper being always more or less conically 
shaped and especially the holes being never entirely perfect at the 
edges. To overcome this drawback each of the taps is furnished 
with a clip which makes the leaking and the pressing-out of the 
stopper quite impossible. Fig. B gives at 5, 6 and 7 three different 
views of such a clip. It consists of two brass rings in the shape 
of a horse-shoe and acting like a spring, so that they can be easily 
fixed round the neck of the tap to fit well. The ring o fits round 
the thinnest part of the tap-stopper, the ring # on the contrary 
round the tube in which the stopper turns, the thick edge of this 
preventing the sliding off. 
As is seen, both rings are provided with two projecting metal lips. 
These lips of the two rings correspond in place and size to each 
other, and are connected by two screws (p), so that they are easily 
adjustable at different distances from each other. It is clear that 
when such a clip is placed on a tap, the stopper can be fixed 
