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II . — List of Plants ivhicli afford Rapliides, Spheeraphides, Long 
Crystal Prisms, and Short Prismatic Crystals. 
By George Gulliver, F.R.S. 
( Taken as read before the Royal Microscopical Society.) 
Having often been asked for the names of tbe plants in which 
these crystals may be most conveniently examined and distinguished, 
probably a short list of them, with a few explanatory remarks, 
would be useful to the students of this interesting and too much 
neglected branch of microscopic phytotomy. At all events, the 
present list is wholly the result of my own researches, and I know 
not that anything like it has ever been published. Figures of the 
different forms of the crystals are given in ‘ Hardwicke’s Science- 
Gossip,’ May 1873, and in the ‘Monthly Microscopical Journal’ 
for December of the same year ; and many of my former memoirs 
on the subject, including extensive observations on the exotic flora, 
are cited in the Royal Society’s ‘ Catalogue of Scientific Papers.’ 
As the microscope is now bidding fair to rival — if not supersede 
— the piano in intelligent families, the present list may form an 
acceptable guide to a supply of materials for pleasure and profit in 
an interesting department of microscopic botany, and this too at all 
seasons ; and the objects are in themselves so beautiful, and their 
preparation and preservation so easy, that slides of them cannot 
fail to become favourites, as they proved to be when Mr. Hammond 
exhibited specimens of the different forms of the crystals at a 
meeting, lately, of the East Kent Natural History Society. 
But, quite independently of mere materials for the microscope, 
plant-crystals deserve far more attention in the cause of science than 
they have yet received. They are lamentably neglected or con- 
founded, especially as regards the diagnostic characters and taxo- 
nomic and physiological significance of the crystals, in our botanical 
and micrograpliical books, which will probably have to be corrected 
by persons who cannot pretend to the rank of botanists. As it 
might appear invidious to specify the prevailing errors, either of 
commission or omission, and the names of their authors, I would 
merely ask the student to consult our current treatises on phyto- 
tomy, micrography, and systematic botany, and then compare what 
is found Wn those books with what he will easily find far more 
plainly in the book of nature. 
To enter fairly, however, on this true book, we must first 
understand clearly the diagnostic characters of the crystals ; and 
these, briefly, are as follows : 
1. Ltapliides . — Small needle-like crystals, with long rounded 
shafts gradually tapering to points at the ends, devoid of angles, 
