— 262 — 



Pontederiaceæ. 

 Monochoria Presl. 



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

 1883, p. 523; M. hastæfolia Presl, Reliq. Hænk. II, 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, Reliq. Hænk. II, p.128. 



var. plantagmea (Roxb.) Solms, Le. p. 524; Hook. f., FL of British 

 India VI, p. 363 ; Pontederia plantaginea Roxb., Fl. Ind. II, 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 End!. 



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

 p. 24; H. australis Miquel, Flora v. Nederl. Indië III, p. 227; Zoster a 

 uninervis Forskål, FL Ægypt.-Arab. GXX 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. 



A s chers on 1 ) and Sauva g eau 2 ) 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 3 ) 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. 



1 ) As cher son, P., 1. c. and: Die geographische Verbreitung der Seegräser in 

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



2 ) S au vage au, C. : Sur la structure de la feuille des genres Halodule et Phyl- 

 lospaclix. Journ. de Botanique IV, 1890, p. 321. 



3 ) Sauvageau, C. : Sur la structure des feuilles des plantes aquatiques. Ibid. 

 p. 46. 



