292 ANNUAL OF SCIENTIFIC DISCOVERY. 



thus turning their numerous pointed lobes towards the north and 

 south. Hence it is called the ' compass plant,' and is useful as a guide 

 across the prairies." Dr. Gray stated, that it is a well-known fact, 

 that leaves ordinarily turn their upper surface to the light ; but ver- 

 tical leaves, as those in question incline to be, tend to take a position 

 which exposes the two surfaces equally to the light of the sun ; and 

 such upright radical leaves, by presenting their surfaces to the east 

 and west, most nearly fulfil this condition. In the specimens of this 

 plant growing in the Botanic Garden, at Cambridge, Mass., the leaves 

 are quite as frequently turned in other directions as towards north and 

 south, or do not present the edges of their leaves in any one plane 

 more than in another. Dr. Gray alluded to the common belief, that 

 the sun-flower turns towards the sun, and said that the fact had found 

 its way into poetry, and out of the domain of science, and is now re- 

 garded in scientific works, as a popular fallacy. The heavy sun- 

 flower stands in unstable equilibrium on its stalk, and is liable to nod 

 by its own weight. Doubtless it is more apt to droop towards the 

 sun than in any other direction, simply on the ground of the sun's ac- 

 tion on a sultry day promoting the exhalations from the side of the 

 stalk on which it shines, wilting it, as it were. But that it follows 

 the sun in its diurnal course, is not believed to be the fact. 



Prof. Morris, of Jackson, Miss., remarked, that in journeying upon the 

 prairies, for several years, he had observed that in running compass lines 

 north and south, the edge of the leaf was seen, so that the plant was not 

 at all conspicuous ; but in running lines east and \vest, the whole plant 

 was seen, and it was a very conspicuous object. The botanical name 

 of this plant is Silphium lacinialum. 



THE ROSE. 



PROF. AGASSIZ, in a lecture upon the trees of America, stated a re- 

 markable fact in regard to the family of the rose, which includes 

 among its varieties not only many of the most beautiful flowers which 

 are known, but also the richest fruits, such as the apple, pear, peach, 

 plum, apricot, cherry, strawberry, raspberry, blackberry, &c. ; namely, 

 that no fossils of plants belonging to this family have eier been discov- 

 ered by geologists ! This he regarded as conclusive evidence, that the 

 introduction of this family of plants upon the earth was coeval with, 

 or subsequent to, the creation of man, to whose comfort and happiness 

 they seem especially designed by a wise Providence to contribute. 



THE MANNA OF THE ISRAELITES. 



AT the conclusion of a paper read before the British Association, 

 by Giles Mumby, Esq., on the " Botanical Productions of the King- 

 dom of Algiers," we find the following passage: "I shall conclude 

 this paper by noticing a lichen called L. esculentus, and which agrees, 

 at least more nearly than any other substance hitherto discovered, with 

 the description of the manna on which the Israelites fed during their 

 wanderings in the desert. This lichen is found on the sand of the 



