244i 



EECREATIVE SCIENCE. 



the Aroidece, of wLich the common Lords 

 and Ladies, Arum maculatum, is a character- 

 istic example, be examined in water, a curi- 

 ous sight will be presented ; of the raphid- 

 bearing cells one after another will be seen 

 exploding and scattering its sharp-pointed 

 missiles, as if engaged in deadly combat with 

 an imaginary enemy. (A clever idea here for 

 our brave volunteers !) The rupture of these 

 cells is due to rapid imbibition of water 

 by the mucilaginous matter they contain, 

 along with the crystals. 



In most of the lily tribe fine acicular crys- 

 tals are formed. The root of the Florentine 

 iris (orris-root) presents large stout ones 

 (Fig. 1, d) ; in the vine, no part appears to 

 be free, even the spiral vessels having been 

 found invaded by them ; in the testa of the 

 seeds of garden balsam groups of them occur. 



Crystals of a shorter form, united in bun- 

 dles, abound in many plants ; in all parts of 

 rhubarb — root, stem, and leaves — they may 

 be readily seen, and the acidity which is so 

 highly prized in the spring-grown shoots for 

 our pies and puddings, is due to the abun- 

 dance of oxalic acid, mostly in crystalline 

 form at that time. Conglomerate raphides 

 of this kind are abundant in some of the 



/5*':- ^K. <t^- 







Fig. 3. — ^A, Cuticle of Indian Fig, with Stellate Ra- 

 phides ; B, some larger ones, from pulpy tissue 

 of the fruit. 



cacti. Every cell of the cuticle of Opuntia 

 (Fig. 3, a) may be seen to possess, and be in 



great part filled, with its bundles of crystals ; 

 in the more pulpy portions of the fruit, 

 where freer room for their development is 

 afforded, they occur not only larger in size, 

 but with much finer and sharper crystals 

 (Fig. 3, b). As some of our friends have 

 been unable to obtain "Eaphides from a 

 Pear," although slides so labelled are to be 

 purchased, we take this opportunity of in- 

 forming any who may not yet have learnt 

 the secret that such are from this source, the 

 Indian-fig cactus, or " prickly pear," as it is 

 sometimes called. In Cactus cochinelUfer the 

 crystals are remarkable for their length and 

 slenderness ; in C. euneagonus they are un- 

 usually large, and look more like flat plates 

 grouped round a central nucleus. 



The two forms of raphides, acicular and 

 conglomerate, seldom occur together ; the 

 flower-stalk of Potlios coriacea, however, pre- 

 sents both in large numbers. In the bark 

 and leaves of species of Tolygonum, Cheno- 

 podium, Atriplex, etc., the conglomerate form 

 is found in quantity. 



Single, solitary crystals are much less 

 commonly met with than either the grouped 

 aciculi or conglomerate bundles ; they occur, 

 however, in bulbs of the onion and shallot, in 

 the bark of the lime-tree, in that of the apple- 

 tree, marked with lines apparently indicating 

 stages of increase, in the testa of seed of the 

 elm, and in that of the seed of black briony 

 {Tamus communis). 



Professor Quekett noticed, that after dis- 

 solving away the earthy salts from the 

 raphides of a cactus, by acid, a cast, as it 

 might be called, was still left in vegetable 

 material, and surprise was expressed at the 

 circumstance. The experiment is a pretty 

 one, and easUy repeated. The bark of the 

 common orache {Atriplex) abounds with 

 them, and from it a few of the crystals may 

 be obtained by tearing up a portion with 

 needles, on a slide. This is to be placed, 

 having added water and a cover, on the stage 

 of the microscope ; with the attention fixed 



