THE AMERICAN MONTHLY 



[January, 



Crystals in Plants. 



If we strip off the outer coverings 

 of the bulb of an onion and examine it 

 with a microscope, it will be found 

 that the cells contain many crystalline 

 masses, made up of prismatic crystals, 

 radiating from centres. These are 

 clearly recognized when polarized 

 light is used, for they will shine out 

 bright when the nicols are crossed so 

 as to give a dark field. Besides the 

 onion, many plants have crystals in 

 some parts of their structure, and they 

 form very good subjects for study. 

 Comparatively, little is known about 

 the crystals of plants. Most of them 

 consist of calcium oxalate, but other 

 compounds are also found ; just what 

 part they play in the economy of the 

 plant, is not known. To the micro- 

 scopist, they afford objects of beauty, 

 while they are sometimes of great 

 service in assisting him to detect 

 adulterations or mixtures of vegetable 

 drugs. 



Crystals of plants are classified in 

 four groups : raphides, sphaeraphides, 

 long prisms and short prisms. 



Raphides are long, slender, needle- 

 like crystals, tapering at both ends, 

 occurring singly or in bundles within 

 the cells. They are usually composed 

 of calcium oxalate, rarely of calcium 

 phosphate. Raphides are abundant in 

 many plants, especially among the 

 Onagraciae. They can be well seen in 

 the leaves of fuchsia,and in asparagus, 

 hyacinths, hydrargia, etc. 



Sphaeraphides are stellate groups of 

 crystals, or globular crystalline aggre- 

 gations. They are very abundant in 

 the common rhubarb, viburnum, and 

 in many of the Urticaceae. 



The dried rhubarb-root, used in 

 pharmacy, will show them in profu- 

 sion. Large groups are also found in 

 the pulp of a ripe pear. 



The long crystal prisms do not, like 

 the raphides, occur in bundles, but 

 singly, or two or more joined together 

 at different angles, as in the onion. 

 These are found in the bulb-scales of 

 the onion, in sweet orris, in the ovary- 



coat of the thistle, and in many other 

 plants. 



Short prismatic crystals are very 

 abundant in the vegetable kingdom. 

 These crystals may be prismatic in 

 shape, or they may be merely cubical 

 and octahedral. They abound in the 

 pericarp of geranium, in the leaves of 

 tradescantia, the common " inch- 

 plant " or "wandering Jew," and in 

 bigonia. 



Plant-crystals are most frequently 

 calcium oxalate, but calcium carbonate 

 is said to be frequently found, and oc- 

 casionally the sulphate, tartrate and 

 malate of the same base, besides other 

 salts. 



Dr. Aser Poll, in a short article 

 recently published,* asserts that there 

 are no crystals of carbonate and sul- 

 phate of lime to be found in plants. 



All crystals insoluble in acetic acid 

 but soluble in mineral acids, (muriatic, 

 nitric, sulphuric acids, etc.,) consist of 

 calcium oxalate. 



Crystals can be best studied in thin 

 sections of those parts of the plants 

 in which they are most abundant. In 

 many cases they can be separated 

 from the cells by washing a freshly- 

 cut surface of a leaf, for example, in 

 water, on the slide. This is fre- 

 quently a very expeditious method of 

 obtaining raphides. Another method 

 of studying them, is to boil the leaf, 

 or other part, in caustic potash, which 

 destroys the soft parts of the plant 

 and the coloring matter, exposing the 

 crystals to view. The tissues may be 

 stained after treatment with the 

 potash solution and thorough washing. 



A New 1-6 Inch Objective. 



BY A. Y. MOORE, M.D. 



A few months ago the Spencers 

 constructed a homogeneous immersion 

 Jp inch objective of 125° balsam angle 

 which was the best they had ever made 

 and it certainly was a lens deserving 

 of praise. 



* Journal Koy,tl Microscopical Society, Ser. 

 2, Vol. 11., p. 598. 



