62 



HUTCHINSON'S POPULAR BOTANY 



white spots on the downy leaves of those curious shrubby plants, the 

 Boehmeria, a tropical genus of the Nettle order. 



Closely allied with crystals are certain by-products of a more adven- 

 titious kind known as " vegetable stones." A large proportion of these are 

 formed and deposited in the tissues from the siliceous and calcareous sub- 

 stances which circulate with the sap. Thus, in the Bamboo, a round stone is 

 found at the joints of the cane, called " tabasheer " ; and in Java and other East 

 India islands, round and pear-shaped stones of carbonate of lime are some- 

 times found in the endosperm (the edible albuminous part) of the coco-nut. 



[E. Step. 



FIG. 91. WALNUT-TREE (Juglans regia). 



This photo shows the Walnut-tree in its winter condition, with the manner of its trunk divisions, and branch 



and twig ramifications. From GREECE to the HIMALAYA. 



In appearance they are almost lustreless, and not unlike a white pearl. 

 They are often as large as cherries and as hard as felspar. The natives of 

 the Celebes put high value on these vegetable opals, using them as amulets 

 and charms against disease. 



Among the other substances which come under the category of by- 

 products may be mentioned the volatile and aromatic oils, so useful in 

 medicine and perfumery. Of these our naturalized and British plants 

 supply not a few, as every one knows who is acquainted with such old 

 favourites as Lavender and Eosemary, Spearmint and Peppermint. Thyme 



