HARDWICKE'S SCIENCE-GOSSIP. 



two portions after the fashion of twin hazel nuts ; or 

 — by far the greater curiosity— a small, but complete 

 egg is contained within the larger one. Upwards of 

 half-a-dozen of these latter monstrosities are, we 

 understand, to be seen in the Royal College of 

 Surgeons. So far as can be ascertained the following 

 account of a duck-egg monstrosity is well-authenti- 

 cated : When opened the shell was found to contain 

 two yolks, and embedded in one of these was a second 

 egg, perfect in every respect, but only about as large 

 as a pigeon's. 



There is on record another instance of a triple egg, 

 but in this case there were three shells, one within 

 the other. We are not in a position to determine 

 whether the account is correct, but there is every 

 probability of its being so. 



T. D. Wright. 



33, Springfield Terrace, Lancastci 



NOTES ON ECONOMIC BOTANY. 

 By J. T. Riches. 



LEGUMINOS/E (GUM ARABIC). —This 

 important gum is the produce of several 

 species of Acacia, natives of Africa. Probably the 

 species most concerned in its production are A. 

 Arabica, Willd. and A. Verek, Guill., although there 



petiole with one gland. Flowers in spherical heads. 

 Pod moniliform. It is from this species, 'or A. Verek, 

 that the pure white gum is obtained. 



A. Verek, Guill. — A small tree, with smooth 

 branches ; spines recurved ; petiole unarmed ; pinnae 

 in 3-5 pairs ; leaflets in 6-15 pairs, nearly lanceolate, 

 blunt ; flowers spiked. 



The gum was formerly imported from Arabia, but 

 now in far the larger quantities from Egypt. It 

 exudes spontaneously, or is obtained by incisions 

 from the bark. It quickly exudes after incision, and 

 hardens in a short time, becoming darker in colour 

 after exudation. In its purest form it occurs in 

 spheroidal tears, varying from J-i inch in length, 

 nearly white, brittle, soluble in cold water. 



Dioscorides makes mention of a useful astringent 

 tree, yielding a white transparent gum, which de- 

 scription, brief as it is, well agrees with the tree 

 yielding this gum ; for the bark of the various species 

 possess astringent and tonic properties. Its uses of 

 course are very numerous. 



It is used in medicine as a mucilage, and, owing 

 to its adhesive nature, it is largely used instead of 

 glue ; it is also employed in calico-printing, as a 

 thickening material for colours and mordants, and in 

 finishing and dressing operations, although gum 

 Senegal, which is the produce of A. Senegal., growing 



Fig. 10. — Root of Jateorhiza palmata. 



Fig. 11.— Acacia Verek. 



is no doubt but what a large proportion of the inferior 

 gum is obtained from A. vera, and other species. 



A. Arabica, Willd. — A small tree 12-14 ^ eet m 

 height ; spiny ; branches and petioles downy ; pinna,' 

 4-6 pairs ; leaflets in 10 pairs, oblong-linear, smooth ; 



about Arabia an 1 the interior of Africa, is most 

 adapted for this purpose, because it yields a thicker 



mucilage. 



The wood of A. vera is said to bz the shittim-wood 



of Scri )ture. 



