402 PROF. J. PERCIVAL ON CALCIUM OXALATE IN ALSIKE. 
parts of the petiole of a leaf there are usually more crystals 
than in the lower part, and transverse sections show a corre- 
sponding difference in the development of fibres at these points. 
Moreover, in seedlings grown in a very damp atmosphere, or 
in the dark, fibres are poorly represented, and the crystals are 
proportionately diminished in number. 
In the cotyledons of the plants there are few or no fibres, and 
crystals are rarely present. I have also noticed that crystals are 
not produced near the finest terminations of the vascular bundles 
or the delicate fibreless portions which connect the main veins, 
but in some species where these narrow connecting-veins are 
thicker, fibres and crystals occur together. It must, however, 
be noted that the absence of crystals in the hypocotyl and root 
of the plants where fibres are common militates against the view 
just expressed, and further work is needed to clear up the 
point. 
I have gone through the vast amount of literature on plant- 
crystals, and am perfectly acquainted with the work of A. F. 
W. Schimper, Kohl, Kraus, Wehner, and others. It appeared to 
me unnecessary to take up space with a résumé of previous work, 
most of which is too speculative to be of value. 
