160 
Oo 
or 
XS) 
Pontederiacez. 
Monochoria Presl. 
5. M. hastata (L.) Solms in De Candolle, Monographia Phanerog. IV, 
1883, p. 523; M. hastefolia Pres], Reliq. Henk. Ul, p. 128; Hook. f., Fl. 
of British India VI, p. 362; Pontederia hastata L., Fl. Zeyl. p. 129. 
Abundant in pools at the mouth of Klong Sarlakpet. 
Area: Ceylon, India, Malaya, China. 
6. M. vaginalis Presl, Relig. Henk. I, p. 128. 
var. plantaginea (Roxb.) Solms, l.c. p. 524; Hook. f., Fl. of British 
India VI, p. 363; Pontederia plantaginea Roxb., Fl. Ind. [I], p. 123. 
Abundant in pools near Lem Dan; Klong Sarlakpet. 
Area of the variety: India, Java; of the main species: Tropical Africa, 
India, Malaya, China, Japan. 
Potamogetonacee. 
Halodule Endl. 
7. H. wninervis (Forsk.) Aschs. in Boissier, FJ. Orientalis V, 1882, 
p. 24; H. australis Miquel, Flora v. Neder]. Indié Il], p. 227; Zostera 
uninervis Forskal, Fl. Aegypt.-Arab. CXX and 157, 1775; ‘Cymodocea 
australis Hook. f., Fl. of British India XI, p. 570. 
The collected specimens are sterile, the leaves very narrow, those 
from Koh Kong 1 mm., those from Koh Chang 0,5 mm. broad. 
Ascherson!) and Sauvageau®”) mention a difference in the struc- 
ture of the leaf-end between the two existing species of Halodule, viz. 
that H. uninervis has a tooth in the middle of the leaf-end besides the 
two marginal teeth, while the West-indian H. Wrightii instead of the 
middle tooth has a kerf, but this difference does not really exist accor- 
ding to my researches. I have examined specimens of both species (H. 
Wrightii preserved in alcohol, from the Danish Westindian Islands), and 
found that the young leaves have three teeth (two marginal besides the 
middle-tooth), but the fullgrown ones have only the two marginal, the 
cells which have formed the middle tooth being destroyed and having 
fallen out, such as Sauvageau®*) has pointed out with respect to various 
other Potamogetonacee. — On the whole it is not possible to distinguish 
the two species when sterile, except using their quite different geographical 
distribution as criterion. 
1) Ascherson, P., lc. and: Die geographische Verbreitung der Seegriser in 
Neumayer, Anleit. zu wissensch. Beobacht. auf Reisen, Berlin, 1875, p. 364. 
*) Sauvageau, C.: Sur la structure de la feuille des genres Halodule et Phyl- 
lospadix. Journ. de Botanique IV, 1890, p. 321. 
5) Sauvageau, C.: Sur la structure des feuilles des plantes aquatiques. Ibid. 
p. 46. 
