108 Harper: Observations on Taxodium 



attention was called by Dr. J. N. Rose to a difference in the bark 

 of cultivated specimens, that of T, imbincarhtm (cultivated there 

 under the name of Glyptostrolms) being considerably thicker and 

 more coarsely ridged than that of T. distichum. On my return to 

 the field I soon found that the same was a constant and well-defined 

 character of the wild trees, and it has since been of considerable 

 assistance to me in studying their distribution, particularly in the 

 winter months when the leaves were fallen. 



There is also a marked difference in the knees, those of T. im- 

 bricariiini being short and rounded, often almost hemispherical, 

 while those of T, disticJuim are usually slender and acute, some- 

 times reaching a height of six feet (in the Suwannee River in 

 Clinch County, for instance). The latter species seems to produce 

 knees much more abundantly, Elliott's opinion to the contrary 

 notwithstanding. In both species the height of the knees and 



w 



that of the enlarged base of the trunk usually indicates the maxi- 

 mum level of the water in which they grow,"^ with the exceptions 

 that in deep ponds the knees of T. imbricarium are entirely sub- 

 merged or perhaps wanting, and in many creek swamps those of 

 Z! distichuvt are very small and do not grow as high as the en- 

 largement of the trunk. In May, 1904, I saw in the pine-barrens 

 near Douglas, Georgia, in a place which had once been a small 

 mill-pond, some saplings of 7! imbricarmm with trunks perceptibly 

 enlarged up to about six feet from the ground, which was just the 

 height of the dam. In cultivation, where they are never inun- 

 dated, it has been my observation that each species produces a 

 slight but characteristic enlargement of the trunk. (The speci- 

 mens on the grounds of the Smithsonian Institution and Depart- 

 ment of Agriculture in Washington are good examples.) This 

 does not agree with the recently published observations of Dr. S. 

 M. Coulter.f In wet pine-barrens, where there is likewise no 

 inundation, the enlargement of the base of 71 imbricarmm, though 

 insignificant compared with what it is in ponds, is always present 

 {s^t figure 4), In any one stream or pond the enlarged bases are 

 all the same height, regardless of the size of the tree. 



* This was noted in the case of T, distichum by Dickeson and Brown in a paper on 

 the cypress timber of Mississippi and Louisiana, in 1S48 (Am. Jour. Sci. II. 5 : 15-22). 

 tRep. Mo. Bot. Gard. 15 : 59.//. 13-18. 1904, 



