b 
a3 
28 MISSOURI BOTANICAL GARDEN, 
But one other species * is known in the western hemi- 
sphere and that is peculiar to South America. 
* SPIRODELA PUNCTATA (Meyer) Thompson. Lemna? punctata Meyer, 
Prim. Fl. Esseq. 262. 1818. Fronds solitary or more commonly 2-4, 
rarely more, successive generations cohering in a regular chain; ellipti- 
cal to slightly obovate-oblong, unsymmetrical, inclined to kidney form; 
1-1.6 mm. wide by 2-3.1 mm. long — averaging about 1.34 mm. by 2.56 
mm. ; thick; obscurely 3-nerved; convex above, frequently with a slight 
protuberance just over the point of the root attachment, flat beneath; 
apex rounded or rarely obtuse; base rounded, prominently winged with 
a narrow membranaceous margin extending almost half the length of the 
frond. Stipe persistent or deciduous, jointed at the peltate attachment to 
the frond. Abundantly punctate over both surfaces with brown epider- 
mal pigment cells. Upper surface with numerous stomata. Roots one, 
two or three, fascicled, long, fragile, brown colored when dry; rootcap 
long and narrow (.18 mm. in diameter by 2.5 mm. long), straight, sharp 
pointed. Spathe ovoid to globose, sac form with opening at the top 
through which project the reproductive organs. Spadix of two stami- 
nate and one pistillate flower. Stamens with long filaments; anthers 
dehiscing longitudinally (?); pollen grains papillose, .021-.023 mm. in 
diameter. Pistil long ovate, slightly compressed; ovule solitary, am- 
phitropous. Fruit lenticular, short and broad, 1 mm. high by 1.2 mm. 
broad; the upper lateral margins projecting into rounded wing-like 
lobes; style short. (Strikingly like a one-seeded fruit of Lemna gibba).— 
Plate 1 B. 
The plants which furnish the original description by Meyer (Meyer, 
G. F. W. Prim. Fl. Esseq. [Introd. page vii.] 1818) were collected about 
1814 in the territory of the Hollandish colonies along the Essequibo 
river in what is now British Guiana, South America. Since that time, 
so far as I can learn, no other collection of the species has been pub- 
lished. Neither Schleiden (Prodromus Monographiae Lemnacearum. 
Linnaea. 13: 392. 1839) nor Hegelmaier (Monograph Lemnaceen. 150, 
1868) was able to learn more of the plant than the original description 
gave. 
My description of the species is based on a collection of the plants, in 
the United States national herbarium, made by the United States South 
Pacific Exploring Expedition under the command of Capt. Wilkes, U.S.N, 
in 1838-42. The specimens were collected at Orange Harbor, on the Tierra 
del Fuego island, at the extreme south end of South America, some time 
between Feb. 18 and April 17, 1839, this being the period of the expedi- 
tion’s stop at Orange Harbor, according to the report of Jenkins. 
Inasmuch as these two localities are so widely separated and since it 
has been impossible to secure either specimens or further publications of 
Meyer’s original plants, some question may arise as to the identity of the 
two collections. Yet in view of the fact that many species of the order 
have even a far wider range, and since the Fuegian plants answer Meyer’s 
8 
