1 882.] Botany. 735 



of a Memccylon, would send out its radicle, which, curving down, 

 formed a flattened disk by which it attached itself to the leaf. 

 But, as if it knew that a leaf could not permanently support a 

 perennial plant, the cotyledons were lifted and turned to the other 

 side, when the end with the disk moved to another place, and in this 

 way, the seed traveled to a more favorable spot. Without reflecting 

 on the observation, Mr. Meehan believed it should be repeated in 

 order to be sure of no mistake. In all plants in our country 

 which fastened to an object through a disk at the end of a rootlet 

 or tendril, as in Ampelopsis and Ihgnouia cafir^I-tta, the attach- 

 ment was made while the disk was forming. A disk once formed, 

 did not reattach itself to an object when removed from the original 

 spot. In like manner the cotyledons, once removed from the 

 endocarps, would have no viscidity with which to form a resisting 

 power while the disk was unfastening itself from its undesirable 

 location. There was, however, so much of singular behavior 

 in the mistletoe family that further observations were very 

 desirable."— Proc. Acad. Nat. Sci. Phila, 



Differences in Radial Thickness in Tree Trunks.— Dr. 

 Stearns in a recent paper read before the Am. Forestry Associa- 

 tion, calls attention to certain differences in the diameters of tree 

 trunks which are well worthy of more extended observation. He 

 asks " whether the greatest diameter is persistently incidental to 

 a certain aspect or quarter of the compass." Professor Whitney 

 found the greatest diameter of the giant trees of California, 

 {Sequoia gigantea) to be twenty four feet, one and one half inches ; 

 this was in a north and south direction. The least diameter was 

 twenty three feet, in an east and west direction. 



Furthermore, a remarkable difference was observed in the 

 lengths of the several radii. The radial length from the heart of the 

 tree to the circumference at its south point was thirteen feet, nine 

 and one half inches (13 ft. 9% in.), while the corresponding 

 measurement north of the heart was but ten feet, four inches 

 (10 ft. 4 in.). The radii making up the east and west diameter 

 were of equal length, that is, eleven feet, six inches (n ft. 6 in.). 



Dr. Stearns suggests that the excess of growth of the south 

 half of the trunk may be due to the greater heat and light which 

 it received. The climate of the site of the tree under considera- 

 tion, the Calaveras grove, is cool, hence the greater heat of the 

 side exposed to the sun was advantageous to it. " In a com- 

 paratively arid region, with a high temperature and infrequent 

 rainfall and a dry atmosphere, we may suppose that the southerly 

 half of a tree might, through excess of _di1 m 1 1 at, suffer from 

 dedicating influences, and make a less growth than the northerly 

 half, as the latter would have the advantage, if advantage it be, in 

 such a climate, of less light and heat and more shade; while in a 

 region less arid, with a much lower mean temperature, etc., the 



