Scientific Intelligence — Botany. 387 



very iiumurous and deep. Very young individuals I have several 

 times found comfortably ensconced in deserted limpet or other shells. 

 The bottom and sides of the cavities occupied by the Echinus be- 

 come in time smoothed and deepened, more particularly in lime- 

 stone ; but this 1 am convinced is not the effect o{ instinctive action, 

 chemical or mechanical, nor of the locomotion of any one individual, 

 but of that of countless generations which have successively inhabited 

 the spots during the lapse of ages, and have thus gradually worn 

 the stone away, and produced the remarkable appearances as of regu- 

 larly bored holes, the depth of which is in many cases increased by 

 the growth of the common millepora around them. — {W. C. Tre- 

 velyan.) 



BOTANY. 

 15. Observations on Manna. By J. Stettner (^Chemical Gazette j 

 July 1848, No. 137, p. 261 ; Archiv der Pharm., vol. liii., p. 194). 

 The author gives the following account of the cultivation of the nianua 

 ash, and the collection of the manna, from observations made in 

 Sicily during the summer 1847. The manna ash, Fraxinus ornus, 

 in the manna districts of Capace, Cinesi, and Fabarotto, where the 

 best manna is obtained, does not form woods, as is generally supposed, 

 but is cultivated in separate plantations. These plantations gene- 

 rally form regular squares, hedged in with Cactus opuntia. The 

 trees are planted in rows, and are from 2 to 8 inches in diameter, 

 with stems from 10 to 25 feet high, which from the first shoot are 

 kept smooth and clean. The soil is carefully loosened, and kept free 

 from weeds. After the eighth year the trees yield manna, which 

 they then continue to do from ten to twelve years, when they are cut 

 down, and young shoots from the roots trained ; one root stock fre- 

 quently yields from six to eight new trees and more. For the pro- 

 duction of the manna, young and strong shoots are requisite ; but they 

 are not tapped before the tree ceases to push forth any more leaves, 

 and the sap consequently collects in the stem. This period is recog- 

 nised by the cultivators from the appearance of the leaves ; some- 

 times it occurs earlier than at others, and the collection of the manna 

 takes place either at the beginning of July or only in August. Close 

 to the soil cross sections are made in the stem, and in the lowermost 

 sections small leaves are inserted, which conduct the sap into a re- 

 ceptacle formed by a cactus leaf : this is the way the manna in sorte 

 is obtained. The incisions are repeated daily in dry weather, and 

 the longer this continues the more manna is obtained. The stems 

 are left uninjured on one side, so that the manna runs down the 

 smooth bark more easily. The next year the uninjured side is 

 cut. The Manna cannelata is obtained from the upper incisions, 

 more than forty of which may be counted on one tree. The sap is 

 there not so fat as below, and consequently dries more easily into 

 tubes and flat pieces. After the manna has been removed from the 

 trees, it has further to be dried upon the shelves, before being packed 



