CONTENTS OF CELLS. 



lie parallel, and have the appearance of bundles of fine needles (figs. 

 37, 38). To the latter, the name of Raphides (pxQis, a needle), or 



acicular crystals (acws, a needle), was originally given. It has been 

 said that these crystals exist also in the intercellular spaces ; but this 

 seems to depend on the mode in which the section of the plant is made, 

 for when raphidian cells (fig. 42 r r r r) are situated close to a lacuna, 

 the crystals may easily be pushed into it accidentally by the knife. 

 Raphides consist principally of phosphate and oxalate of lime. They 

 abound in some plants, especially Cacti, and they 

 are common in Squill, and in the officinal Tur- 

 key Rhubarb, which owes its grittiness to their 

 presence. One hundred grains of rhubarb root 

 contain about 30 or 40 grains of oxalate of lime 

 crystals. Acicular crystals may be easily seen by 

 making a section of any Liliaceous plant, as the 

 hyacinth, and spreading the thick mucilaginous 

 matter of the cells on the field of the micro- 

 scope. Radiating raphides are seen in the sepals of Geranium robertia- 

 num and lucidum; the crystals, consisting of oxalate of lime, fill the 

 whole of the cells in the middle of the sepal, their size varying from 

 Woo to T 3oo f an inch. Quekett found them in all the species of 

 Pelargonium and Morisonia that he examined, and he thinks that they 

 are as general as the beautiful markings in the cuticle of the petals of 

 these plants. Clustered crystals have been detected in Malvaceous 

 plants, and in the sepals of the strawberry; numerous acicular crystals 

 have been observed in Fuchsias, and solitary cubical crystals in the 

 superficial cells of the sepals of Prunella vulgaris and Dianthus Caryo- 

 phyllus. In the outer covering of the seed of Ulmus campestris, the 

 sinuous boundaries of the compressed cells are traced out completely 



Fig. 38. Cells of Aurum maculatum. Clusters of raphides in a large oval cell surrounded by 

 smaller cells. 



Fig. 39. Cellular tissue, from leaf of Flcus elastica. c, A large cell, r, An agglomeration of 

 crystals suspended in a sac by a tube, t. u, Utricles filled with grains of chloropliylle. 



Fig. 40. Cells of Beet with conglomerate radiating crystals, a. b, Separate crystals of different 

 forms. 



Fig. 41. Conglomerate crystals of oxalate of lime from Rhubarb. 



Fig. 42. Cellular tissue of Colocasia odora. c c, Cells with grains of chlorophylle. rrrr, Ra- 

 phidian cells projecting into a lacuna or intercellular space. 



