[J2)ril, 1859.] 97 



ON THE SITUATION OF RAPHIDES. 



The calcareous concretions in the cells of plants known by the 

 names of raphides and cystoliths, afford very interesting objects 

 to the microscopist. The former are to be found in the cells of 

 most plants, and are particularly abundant in the Cactus tribe ; 

 the latter are most plentiful in the XJrt'icaceae. and the Acan- 

 thacea. Some discussion has taken place as to the situation in 

 which the raphides are found. There is no doubt that they 

 occur in all parts of the plant, but the point in dispute is 

 whether they are always situated in cells, or whether they occur 

 also in the intercellular passages. Raspail has stated that they 

 are to be found in the intercellular passages, but Mr. Quekett, 

 in his valuable lectures on Histology, asserts that Raspail is in 

 error, and that the raphides are always in the interior of cells. 

 This statement of Mr. Quekett is adopted by Dr. Carpenter in 

 his book on the microscope. Mr. Henfrey, in the ' Micrographic 

 Dictionary,^ however, says : — " They (raphides) are usually found 

 only in the interior of the cavities of cells, but in some cases 

 they occur in the intercellular cavities, perhaps, however, acci- 

 dentally." An instance has come under my own observation 

 in which these bodies were undoubtedly situated in the intercel- 

 lular cavities, and in which I can see no reason for supposing 

 their occurrence in that situation to be accidental. I found, in a 

 shallow part of the Thames, near Weybridge, a stem of Myrio- 

 phyllum (probably Myriophyllum verticillatum) , which, being co- 

 vered with a minute Alga, I took home, wishing to examine the 

 latter. Upon making thin transverse sections of the stem, and 

 placing them under the microscope, I observed that the inter- 

 cellular cavities contained an abundance of stellate raphides, 

 such as are shown in the sketch on p. 98. The tissue of the 

 Myriophyllum stem consisted of a central cylinder of very small, 

 delicate cells ; the outer layer consisted of much larger cells ; 

 and the central cylinder and the outer layer were united by radii 

 or spokes, each formed of a single row of oblong cells, the whole 

 section thus presenting exactly the appearance of a wheel. The 

 sketch shows a segment of one of these wheels, and it will be 

 seen by referring to it that the intercellular cavities are very 

 large, and that the raphides are situated in these cavities, and 

 rest upon the spokes of the wheel. It will be seen that not 



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