i 3 o 



HARD WICKE'S SCIENCE -G OSSIP. 



The remarks may at first appear to be of little 

 interest, but in putting them forward it is with the 

 hope that they will teach us to at least take pre- 

 cautions to protect or remove such an unpleasant 

 enemy from some of the most beautiful works of 

 art. H. T. Johnston-Lavis, 



ON PREPARING AND MOUNTING LEAVES 

 AND OTHER PARTS OF PLANTS TO 

 SHOW THE CRYSTALS IN SITU. 

 By W. H. Hammond. 



EVER since I first began to use the microscope 

 Plant Crystals have been objects of interest 

 to me, not only on account of their great beauty as 

 "objects," especially with the polariscope, but also 

 because they open a new and comparatively unex- 

 plored region of phytotomy ; in fact, except in Pro- 

 fessor Gulliver's writings, they are hardly mentioned, 

 or very summarily dealt with by other botanical 

 writers. At first I used to be content with a sight of 

 them after boiling and mashing parts of plants, but I 

 soon became dissatisfied with this method, and began 

 to look about for some means of examining the 

 crystals just as they grew in the different plants ; for- 

 tunately I happened to look at a back number of 

 Science-Gossip (January, 1875), and came across a 

 paper by the late Dr. Beatty, " On Decolouring and 

 Staining Vegetable Tissues for Microscopic Ex- 

 amination " ; other papers, by Dr. Beatty, came out 

 afterwards, and I gathered many valuable hints from 

 them oh the subject. 



I am often asked how my preparations are made, 

 so I will describe my process of preparing and 

 mounting, for the benefit of other workers with the 

 microscope who are interested in these beautiful, 

 but much neglected, marvels. 



The first thing to be done is to get the bleaching 

 solution, and this may be very easily prepared as 

 follows : — Equal weights (say four ounces) of chlori- 

 nated lime and common washing soda, both in fine 

 powder, are put into a half-gallon bottle of cold 

 water, and well shaken together, then left to stand 

 till the fluid is quite clear, this is poured off gently 

 into another bottle, and a strong solution of washing 

 soda added as long as a white powder is thrown 

 down. The mixture is again left till clear, and then 

 poured off; this is the bleaching fluid. The original 

 substances in the first bottle may be again treated with 

 cold water. Leaves and other tissues are kept in this 

 fluid till bleached and semi-transparent, large or thick 

 leaves should be cut up into small pieces. I find the 

 small, round night-light glasses, which may be bought 

 for a penny each, are very convenient for bleaching 

 the tissues in, and also for the dyeing and subsequent 

 soakings, covering them over with pieces of glass to 

 keep out the dust. It is not always convenient to 



prepare and mount leaves directly they are gathered, 

 so I always carry with me a small account-book, 

 interleaved with blotting paper, and with an elastic 

 band round it ; leaves are put into this when gathered, 

 and by carrying it in the breast-pocket of the coat, 

 they are soon dried by the warmth of the body ; in 

 the summer time several books full of leaves are col- 

 lected, ready for the long winter evenings. Dried 

 leaves will bleach sooner than fresh-gathered ones. 



Having bleached some leaves (the time it takes to 

 do this varying very much), they must be well washed 

 in warm water in basins or pie-dishes, changing the 

 water often for about two days, and brushing the 

 tissues with soft camel-hair brushes. I often find it 

 of use to put the plant tissues into acetic acid and 

 water for about a minute before the final washing, 

 but acids must be very cautiously used, or the crystals 

 may be dissolved. 



The leaves or tissues are then ready to go into 

 either of the following dyes : — 



The carmine dye is prepared partly according to 

 Dr. Beales's formula, viz. : — 



Carmine 20 grains. 



Strong liquor ammonite ... \ dram. 

 Pure water 4 ounces. 



The carmine is heated in a test tube with the am- 

 monia till dissolved, and then added to the water in 

 a bottle and well shaken, and left to settle or be 

 filtered. The dye should smell strongly ammoniacal. 

 Sections are soon dyed in the above, but leaves take 

 several days, or a week or more. Sections of the 

 India-rubber plant leaf, or of the common fig, dyed 

 in carmine, will show the stalked crystals, called 

 cystoliths, very nicely ; pieces of the leaves of the fig, 

 hop, nettle, wall-pellitory, or wych elm, dyed, will 

 show the cystoliths when viewed from above or 

 below. I generally mount two leaves or pieces on 

 the same slide, one with the superior and one with 

 the inferior surface uppermost. 



The logwood dye is prepared according to the 

 prescription in Rutherford's " Histology." 



A. Make a saturated solution of calcium chloride 

 in 70 per cent, alcohol, and then add alum to 

 saturation. 



B. A saturated solution of alum in 70 per cent, 

 alcohol. 



C. Add A to B in the proportion of one to eight. 



D. A barely alkaline saturated solution of logwood 

 in water. 



Add D to C till a deep violet-coloured dye is 

 obtained. 



I make D by boiling logwood chips with water 

 and a very little potash, then filtering. 



I generally use methylated spirit where alcohol i< 

 recommended. 



The leaves and tissues may be immersed in either 

 of the above dyes, straight from the last wash-water, 

 and will be dyed in either in about the same time. 



