\ 
1890.] The Knees of the Taxodium distichum. 333 
THE KNEES OF THE ZAXOD/IUM DISTICHUM. 
BY ROBERT H. LAMBORN. 
N a“ Preliminary Notice of Some of the Results of the United 
States Geological Survey Examination of Swamp Land,” by 
Prof. N. S. Shaler, of Cambridge, Mass. (Science, March 8, 89), 
it is stated as the result of observations begun in 1874, while en- 
gaged on the Kentucky State Survey, and continued and recorded 
in various publications by the author, official and otherwise, ex- 
tending up to date, that the occurrence of knees on the Taxodium 
distichum is explained “through a need of an aeration of the sap 
which is denied the roots that are under water.” He also ascribed 
the enlarged base of the tree to the same need of aeration of the 
sap, and discards as disproven the hypothesis that such enlarged 
or buttressed base is useful to the tree as securing greater resist- 
ance to storms. 
In the Memoir (by the same author) of the Museum of Com- 
parative Anatomy (Harvard College, 1887), the theory of aeration 
is still more distinctly enunciated. “The failure of knees to de- 
velop when they grow on high ground; the development of the 
knees when the roots are in permanent water; the rise of the 
knees above permanent water level, and to a height varying with 
that level, and, finally, the destruction of the trees whenever the 
level of permanent water rises above the tops of the knees,—these 
facts incontestably show that there is some necessary connection 
between them and the function of the roots, when the latter are 
permanently submerged.” “It seems likely, therefore, that some 
process connected with the exposure of the sap to the air takes 
place in these protuberances.” Following these official publica- 
tions, a communication was presented to the Academy of Natural 
Sciences, of Philadelphia (pp. 67 to 69, Proceedings, April, 1889), 
by Prof. Wilson, of the University of Penna., in which the result 
of certain observations made by him in Florida in 1885-6 are 
given. He records a careful series of experiments made by dig- 
. 
