100 262 



Pontederiaceæ. 

 Monochoria Presl. 



5. M. hastata (L.) Solms in De Gandolle, Monographia Phanerog. IV, 

 1883. p. 5:23; M. hasfæfolia Presl. Reliq. Hænk. 11. 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 Pres). Reliq. Hænk. II, p. 128. 



var. plaütagioea (Roxb.) Solms, I.e. p. 524; Hook. f.. Fl. of British 

 India VI, p. 363 ; Pontederia plantaginea Roxb.. Fl. Ind. Il, 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. 



Potamogetonaceæ. 

 Halodule Endl. 



7. H. unlnervis (Forsk.) Aschs. in Boissier. Fl. Orientalis V, 1882, 

 p. 24; H. australis Miquel, Flora v. Nederl. Indie 111, p. 227; Zostera 

 tiniuervis Forskål, Fl. Ægypt.-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. 



As cher s on ^) and Sauvageau-) mention a difference in the struc- 

 ture of the leaf-end between the two existing species of Halodule, viz. 

 that H. uninevvis has a tooth in the middle of the leaf-end besides the 

 two marginal teeth, while the West-indian H. Wricjhtii 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. 

 Wrif/htii 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 Potamogetonaceæ. — On the whole it is not possible to distinguish 

 the two species when sterile, except using their quite different geographical 

 distribution as criterion. 



') Ascherson. P., 1. c. and: Die geographische Verbreitung der Seegräser in 

 Neumayer, Anleit. zu wissensch. Beobacht. auf Reisen, Berhn, 1875, p. 364. 



*) Sauvageau, C: Sur la structure de la feuille des genres Halodule et Phyl- 

 lospadix. Journ. de Botanique IV, 1890, p. 3-21. 



') Sauvageau, C: Sur la structure des feuilles des plantes aquatiijues. Ibid. 

 p. 46. 



