— 240 — 



are to be found in the Herbarium of the Botanic Garden at Copenhagen 

 labelled by Hornemann: „Sub nom. Lemnae accepi ex Ind. occid. — an 

 Marsilea vel Azolla?" 



This pretty little Halophila which I have named in honour of the 

 German botanist professor P. Ascherson who has added so much to the 

 knowledge of the genus, is nearest to H. Engelmanni Aschs. from Florida, 

 but the latter is taller and has lanceolate to linear-lanceolate leaves, 3 

 pairs together on the top of the shoot, and many more transversal ribs. 



As I am preparing a little monograph of the genus Halophila, I 

 should be very glad if botanists would send me plants for revision, as 

 well as specimens dried up as specimens prepared in alcohol. — The genus 

 consists only of 8 species, but they are very interesting both from a 

 morphological and from a geographical point of view. I should think that 

 the following division of the genus would prove to be a natural one: 



1. Spinulosae. Rhizome with scales, the erect shoots with numerous 

 pairs of leaves, arranged as in Potamogeton densus, leaves sessile elliptic 

 or obovate with oblique base and with dentate margins. 



H. spinulosa (R. Br.) Aschs., China to Australia. 



2. Americanae. Rhizome with scales, the erect shoots with one 

 pair of scales and 2 or 3 pairs of leaves, arranged in a verticillaster ; 

 leaves stalked, lanceolate or elliptic with dentate margins. 



H. Engelmanni Aschs., Florida; H. Ascher sonii Ostf., St. Croix. 



3. Tijpicae. Rhizome with scales, the erect shoots with one pair 

 of leaves and without scales; leaves stalked, lanceolate or ovate with 

 dentate or entire margin. 



H. ovalis (R, Br.) J. D. Hook., from the Red Sea to the Pacific Ocean; 

 H. stipulacea (Forsk.) Aschs., the Red Sea and the Western Part of the 

 Indian Ocean; H. decipiens Ostf., n. sp., the Gulf of Siam l ) ; H. Baillonis 

 Aschs., West Indies. 



4. Pusillae. Rhizome -without scales, but with leaves; leaves stalked 

 „with sheathing, auricled base" (according to Ascherson & Gürcke in Engler, 

 Natürl. Pflanzenfam. II, 1, p. 249). H. Beccarii Aschs., Arakan and Borneo. 



The Botanic Museum of Copenhagen, -November 1901. 



] ) v. p. 260. 



