130 



layers. The upper layer was seven inches thick, and was laid hot, 

 rolled down, p.nd thoroughly cooled four years ago. Below tliis there 

 was an old floor of tar and gravel, six inches thick. A. curious bulge in 

 the floor was first noticed, covering about a square foot. In six hours 

 the floor was burst open, and a perfectly formed toadstool, with a 

 stem two inches through and a very wide cap, made its appearance. 

 Elsewhere the floor was smooth and unbroken. 



* T/ie Sweet Potato. — In a paper which he has kindly sent us, M. 



DeCandolle calls attention to a character in the sweet potato plant 

 .to which sufficient attention has not been paid by systematists, and 

 that IS the radical tubercles ("sweet potatoes "), which exist in no 

 other plant of the order Convolvulaceae. " In fact," says the author, 

 " the dilated portions of Convolvulus Jalapa, C. pentaphyllus, C. 

 Scammonia, etc., are caudices or rhizomes, as we may easily satisfy 

 ourselves from figures worthy of confidence published in different 

 works. I shall not stop to question whether in these species the 

 expanded pordon is the base of the stem or the principal root or a 

 combmation of both, this depending much on the character which 

 we choose for distinguishing root from stem. It is sufficient to point 

 out as a fact that in the sweet potato the expansions belong to lateral 

 roots, while in the other species mentioned, it is the primary axis 



. that becomes a tubercle. This difference is connected with other 

 and greater ones. The roots of the sweet potato {Convolvulus 

 Batatas, L.; Batatas ediilis, Choisy) consist especially of a cellular 

 tissue filled with fecula, and have a saccharine taste. The axillary 

 tubercles, on the contrary, offer a remarkable complication of vessels 

 and cells which secrete resinous matters. The sweet potato is good 

 to eat, but tlie other roots, like the rhizomes of scamraony, are 

 eminently purgative. Generally, in this family, what belongs wholly 

 or in part to the stems is more or less purgative, as the stems of 

 Convolvulus Sepium formerly employed. * * * Whether we 

 adopt the genus Batatas of Choisy, or whether we reject it, with Meiss- 

 ner, or as xMessrs. Bentham and Hooker have done in their Genera, the 

 peculiar and rare character of the roots of the sweet potato should be 

 in some way made prominent, and it appears to be 'impossible to 

 leave the plant immediately along side of the jalap. * * * The 

 geographical origin of the sweet potato is still a problem. I have 

 tried to solve it in a work now in press, entitled Origin of Cultivated 

 Plants. The probability is in favor of an American origin but there 

 are very smgular reasons for considering the question as doubtful." 

 The Gymnocladus as a Fly- Poison.— ^ Virginian correspondent 

 of the American Agriculturist asserts that the male trees of the Ken- 

 tucky coffee-tree {^Gymnocladus Canadensis) have been long observed 

 by him to be a sure insecticide. He says : "Back of our house 

 here and overhanging the piazza, is a very large coffee-tree. Though 

 this locality is infested, like Egypt, with a plague of flies, we have 

 never suttered any serious annoyance from them One year this 

 tree was nearly stripped of its leaves by a cloud of potato-flies (the 

 bhstering fly), and we feared that the tree would die from the com- 

 plete defoliation. In three days, the ground beneath was black with 

 a carpet of corpses, and the tree put out new leaves and still flourishes. 



