1888.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM 461 



tiuctly the spots called after Caspary. Xo indication of mechanical 

 tissue was to be observed in the tuber. 



If we now turn to the description of our plant as given by the early 

 authors anil compare it with what has been shown here, we shall find 

 that Michaux's " radice tuberosa" is to be regarded as an old tuber 

 that has developed a plant, and Pursh's "herba glabra tuberosa"' 

 shows the same, and evidently he had seen more than a single tuber, 

 since he has described not only the "radix" but the plant as being 

 "tuberosa," and we suppose the same of Eaton's "tuberous." But as 

 to the description of the stolons and runners, it is not sure whether 

 what Torrey describes as "suckers" should be regarded as stolons or 

 not, when a sucker, according to Gray's " Structural Botany," 1830, is 

 "rising from a subterranean creeping base," and, as it has been shown 

 above, our plant has no " suckers." " Darlington's filiform runners, 

 from the axils of the leaves," may be nothing but the true runners ; but, 

 on the other hand, he does not mention if he has observed them in the 

 .axils of the upper leaves or where, and it might not be improbable that 

 he had seen the base of the stolons also, but with the tubers broken 

 off. Chapman's "stoloniferous" seems certainly to show that he has 

 •observed the presence of the true stolons, and it is a question why 

 he did not mention the runners. 



U. S. National Museum, Washington, December, 1888. 



EXPLAXJTIOX OF PLATES. 



Hydrocotyle Americana L. 



Plate XLVI. 



Fig. 1. The lower part of the plant, developed from a tuber, with stolons ending in 

 tubers. 

 2. The upper part of the plant, with two runners. 

 3, 4. A scale-like leaf from a stolon, seen from the front and back. R., roots. 



5. A scale-like leaf from a stolon, supporting a branch with its first leaf L. R., 



roots. 



6. A scale-like leaf from a stolon, supporting a branch with a leaf of the same 



shape as those of the stem. R., roots. 



7. An old tuber, having developed a plant. Two stolons, ending in tubers, 



are to be seen, of which the one has been developed from the axil of the 

 uppermost scale-like leaf of the old tuber. 



8. A young tuber of the most common shape. 



9. A young tuber just formed. 



Plate XLVII. 



10. A young, very long tuber, consisting of six interuodes. 



11. A young tuber with a smaller one, developed from the axil of one of the 



lower-situated scale-like leaves. 



12. Leaf of a tuber. 



13. The development of a stolon, at the summit of which the bicleft leaf is to 



be seen. 



