300 BOTANY OF SOCOTRA. 



lately Baron Mueller lias sent me a very similar plant (also without fruit) 

 from Australia, which, he says, has very rarely subcoriaceous leaves, but it 

 has only been gathered twice by Professor Wilson. 



2. P. fluitans, Eoth Tent. Flor. Germ. i. 72 ; Boiss. Flor. Orient, v. 16 ; 

 Eeichb. Ic. Flor. Germ. vii. t. 49. 



Socotra. B.C.S. n. 733. 



Distrib. Widely spread in temperate and tropical regions. 



Quite the north African (Algeria) form of this plant. There is no fruit, 

 but I think the above is correct. In the substance of the leaf, African 

 specimens are one extreme, European the other, south American coming about 

 half-way between. 



2. P. pectinatus, Linn. Sp. 183 ; Kunth Enum. iii. 137; Ach. Kich. Tent. 

 Flor. Abyss, ii. 354; Boiss. Flor. Orient, v. 18; Eng. Bot. t. 3422. 



Socotra. In streams. B.C.S. n. 176. 



Distrib. Almost cosmopolitan. 



This has just the habit of the east European specimens "from saline lakes " 

 in Hungary, Lithuania, and Caucasus. 



Specimens from Austrian Tyrol, gathered by Baron Hauseman and dis- 

 tributed by Huter as "P. marinus, L.," match the fruit of the Socotran 

 specimens very nearly. I had called this var. pseudo-marinus, but it is perhaps 

 hardly worthy of a varietal name. 



2. EUPPIA. 

 Ruppia, Linn. Gen. n. 175 ; Benth. et Hook. Gen. PL iii. 1014. 



A genus of one species subject to some variation, found in salt and brackish 

 waters over nearly the whole world. 



R. maritima, Linn. Sp. 184; Kunth Enum. PI. iii. 123.' 



R. spiralis, Dumort. Flor. Belg. 164; Boiss. Flor. Orient, v. 19. 



R rostellata, Koch in Reich. Crit. ii. 66, t. 174, f. 306 ; Boiss. Flor. Orient, v. 20. 



Socotra. In streams near Galonsir. B.C.S. n. 445. 

 Distrib. Of the genus. 



I do not find it possible to recognise as distinct the several forms of this 

 plant which have been described as species. 



3. NAIAS. 

 Naias, Linn. Gen. n. 1096 ; Benth. et Hook. Gen. PL iii. 1018. 



A small genus of fresh-water plants found over tropical and temperate 

 j.'egions. 



