1888.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 457 



Achille Richard in his Monographic du genre Hydrocotyle;* but he says 

 only: "Elle (fl". Americana) a, selon Michaux, une ratine tub6reuse." 



Of all the species mentioned in De Candolle's Prodroinust only JIi/- 

 drocotyle interrupta Muhl. was described as being tuberous, namely its 

 variety tuberosa : " Caule hinc inde ad nodos tumido et tuberoso " 

 which tuberosity then is quite different from that of H. Americana, 

 and nothing has been written about the tubers of our plant. Eatoni 

 is another American author who has mentioned it as "tuberous " but 

 from his observation in 1833 until 18SG the plant does not seem to have 

 been observed as being " tuberosa" nor "tuberiferous." 



The stolons, Vasey's "tuberiferous threads," seem to have been 

 knowu before, for Torrey§ has described the plant in this manner: 

 " Stems with long suckers." It has also been mentioned by Darling- 

 ton || as having "Filiform ruuners from the axils of the leaves," and 

 further by Chapman,^} who has called the stem " stoloniferous ; " but 

 these remarks are all that we know about them, and it is not perfectly 

 sure that these authors have intended to describe the true stolons 

 since they may have seen only the runners of the plant. 



On turning to the specimens of Hydrocotyle Americana, it is first to 

 be remarked that the plants, which I have had the opportunity of ex- 

 amining from the Eastern Branch, and others from different places pre- 

 served in the herbaria of the U. S. National Museum and of the De- 

 partment of Agriculture, all the complete individuals show that they 

 have been developed from tubers. ■ The development from the seed is 

 not known, but it is to be supposed that there is little difference between 

 this and theotber method, exceptiugthat it would beiuterestingtoknow 

 whether the primary root has a tendency to be tuberous. There is no 

 doubt that the plant is able to propagate itself by seeds, for many of 

 the specimens I have seen bore fruits which "were all normally devel- 

 oped. Plate xlvi, Fig. 1, illustrates the lower part of the stem of Hy- 

 drocotyle Americana, and shows the tuber from which the plant has been 

 developed. We see that the rhizome consists of the tuber and a single 

 internode, bearing a scale like leaf, from the axil of which a long 

 stolon has been developed; we see further that another branched stolon 

 has been developed from the axil of the lowest complete but now faded 

 leaf of the stem. From the axils of the other leaves at the upper part of 

 the stem we see (Plate XLvr, Fig. 2) that two runners have been de- 

 veloped, and at the summit of the stem we find the inflorescence, which 

 is not figured, since it is already well known. 



It will be observed that our plant has two kinds of vegetative 

 propagation: by stolons, ending with tubers, and by runners. Now, it 



*Anu. sc. phys., IV, Tab. 55, Fig. 10, 1820. 



tA. P. DeCandolIe: Prodromus syst. nat. regni vegetal)., iv, 1830. 



t A. Eaton: Manual of Botany for North America, 1833, p. 180. 



§ John Torre,; : Natural History of New York, Part I, 1843, p. 262. 



|| William Darlington: Flora Cestrica, 1853, p. 99. 



If A. W. Chapman: Flora of the Southern United States, 1383, p. 158. 



