29 



ings and preparations, that the so-called mealiness of these plants 

 is produced by simple hairs of two or three cells, the terminal cell 

 being dilated into a globular vesicle, numbers of which so reflect 

 the light as to produce the mealy appearance. By transmitted 

 light they appear colourless and transparent. The dilated terminal 

 cell is about 1 -266th of an inch in diameter. 



Calcareous granules on Bryonia cZ/o/ca.— These, commonly de- 

 scribed by botanists as "asperities" or " callous points," he proved, 

 by extemporaneous preparations and experiments, should be rather 

 called Calcareous granules ; for this is their true nature, as they 

 are composed of carbonate of lime. Each callous point is about 

 1-1 14th of an inch in diameter, and the smooth, shiny, constituent 

 granules composing that point have an average size of l-666th of 

 an inch. This profusion of calcareous matter on the surface of the 

 leaf of bryonia is remarkable, as this plant is generally devoid in- 

 ternally of any raphides, and contains an unusually small number 

 of other saline crystals. 



Sphccrapkides and Epidermis of the leaf oj the Tea Plant. — The 

 public mind being now much interested about the adulterations of 

 tea, the Hon. Sec. gave some demonstrations, and exhibited pre- 

 parations, of the leaf of a fresh plant of Thea viridis. The epider- 

 mis on both sides of the leaf was shown to be composed alike of 

 cells with sinuous margins (colpenchyma), with the addition on the 

 epidermis of the under surface of oval stomata, and shortish, smooth, 

 taper, slightly curved hairs. Throughout the parenchyma of the 

 leaf were sphseraphides, thickly studded, and with a mean 

 diameter of about 1-1 000th of an inch ; and here and there were 

 short strings of similar sphseraphides, only about half as large, on 

 the fibro-vascular bundles. The composition of the sphseraphides 

 appears to be chiefly oxalate of lime. They are not easy to find, in 

 consequence of the density and opacity of the surrounding parts ; 

 and this is probably the reason why these beautiful crystals have 

 hitherto escaped discovery. 



Value of Potass in Histological Phytotomy. — At the same time he 

 remarked that the value of potass in separating the fibres, mem- 

 branes, or cells, and clearing parts of plants for microscopical inves- 

 tigation, seems to have been insufficiently appreciated. He showed, 

 for example, that by treatment with cold solution"of this alkali, 

 and still better by boiling in it portions of the tea leaf, the 

 epidermis could easily be detached from both sides, leaving quite 

 distinct the intervening layer of parenchyma and nerves, and thus 

 beautifully exposing the sphasraphides. He had found the potass 

 equally useful in disclosing the short prismatic crjstals in legu- 

 minous and many different orders of plants, and in examination of 

 the tea of commerce ; so that the heretofore refuse of the teapot 

 may be made a very interesting subject for microscopical inquiry. 



