Objects for the Microscope. 19 



or remains of organic matter may have made a little soil. 

 These roots spread out and ramify into the most minute 

 crevices, breaking up the lava into small fragments, and 

 finally rendering it fit for culture. 



LITHOSPERMUM. 



From lithos, a stone, sperma, a seed. 



The hardy stony seeds have given it this name, as well 

 as the old English appellative Gromwell, from the Celtic 

 grom, a seed, and mil, a stone. 



The leaf of this common plant is extremely beautiful ; 

 the hairs are not only bulbous as in borage, but cells are 



frouped around the base of each like a circlet of crystals, 

 here are three species worth seeking : 



The common white L. arvense, in cornfields. 



L. officinalis, pale yellow. 



L. purpurea, large blue flowers in chalky soil. 



RAPHIDES. 



These are crystals found in the cells of various plants. 

 No better example can we have than the 



CUTICLE OF HYACINTH, 



in every cell of which we see a cylindrical crystal. Exa- 

 mined with polarized light they are most distinctly seen, 

 and enable us to understand the position of raphides in 

 other plants. The Cactus, the common Dock, and various 

 other vegetables, have bundles of needle 7 shaped crystals 

 in their cells. Turkey Rhubarb and the garden Rhubarb 

 have rectangular prisms of carbonate of lime grouped in a 

 stellate form. See the slide of 



RAPHIDES FROM RHUBARB. 



What their use is we do not know. Another kind called 

 cystolithes, are stalked and suspended in the cells of the 

 nettle tribe. Their formation has been watched : first a 

 little papilla or swelling is perceived at the upper part of a 

 cell, which increases at the end into a clubbed form, from 

 which crystals of oxalate of lime sprout forth. 



