346 Variations in the Cotyledons and 



dead, and the proboscis lying at some distance. Fully twenty- 

 four hours elapsed before I could examine it farther, when, 

 to my astonishment, the proboscis was seen to contract and 

 dilate its aperture with energy ; yet the body itself had soft- 

 ened, and could not be lifted even on a hair pencil. 



Planaria cornuta was discovered by Miiller ; but I know 

 his animal only through the short and imperfect description 

 given in Dr. Turton's translation of the Systema Naturce^ 

 vol. iv. p. 65. There are some discrepancies between it and 

 mine ; but I think the characters in common are sufficient to 

 show the identity of the species. Still I shall feel indebted to 

 any one of your readers who may have access to the Zoologia 

 Danica^ if, by a comparison of the figures, he shall confirm 

 my synonyme, or prove that it is erroneous. 

 1 am, Sir, yours, &c. 



George Johnston, M.D. 

 Bermichupon Tweedy Jan, 28. 1832. 



Art. XI. On Variations in the Cotyledons and Primordial Leaves 

 of the Sycamore (AVer Pseicdo-Flatanus L.). By the Rev. J. S. 

 Henslow, A.m., King's Professor of Botany in the University 

 of Cambridge. 



Sir, 

 The number of cotyledons in coniferous plants is well 

 known to be very variable, and the seeds of some other 

 dicotyledons have likewise been observed occasionally to 

 possess more than two. The sycamore ( A^cer Pseiido-Pla- 

 tanus X.) is a good example of this fact; and a careful search 

 among the numerous young plants which every where spring 

 up in the neighbourhood of this tree, has afforded me many 

 specimens in which the cotyledons were either three or four 

 in number. In some instances, where there were only two 

 as usual, one of them was more or less cloven down the 

 middle {^g. 80. a); and these served to illustrate, in a marked 



manner, the way in which 

 others had become pos- 

 sessed of more than their 

 ordinary number. For in 

 these cases either two of 

 the cotyledons were not 

 at first so large as the 

 ^0 third, when there were 



three only {b) ; or else, when four were present, they were all 

 proportionably smaller than in those plants which bore two 



