369 



WELWrTSCII'S AFRICAN MARINE ALG.E. 



By Ethel 8. ]>ahton. 



(Plate 373.) 



[Most classes of the Angolan Algne are in general less abundant 

 than in the extra-tropical zones, and they diminish in number of 

 species from the littoral regions towards the mountainous country 

 in the interior, until further inland the highlands are reached, 

 where, with the necessary exception of the marine genera, the 

 greatest number of species were found. 



Among the DcsmiiUacca;, Pt'niuiii Diijitus Breb. and Clostenum 

 Lunula Ehrenb. are particularly abundant in stagnant pools in the 

 coast region, Cladophora is a prevalent genus both in fresh water 

 and in the sea ; the species of Oscilhitoiiit appear to be scarce in the 

 rainy districts. In the highland region various species of Scyto- 

 neina are produced in enormous quantities and of many colours ; it 

 is a species of this genus which when prodigiously multiplied causes 

 the black colour of the rocks of Pungo Andongo, commonly called 

 Pedras Negras. Towards the interior of Angola species of Scyto- 

 nema are found which cover extensive tracts with a red or rusty 

 colour, and some of them are very frequent in the highlands 

 of Pungo Andongo and on the plateau of Huilla, and there in- 

 numerable plants of Ut lie ill (Ilia, Eriocaulon, Isoetes, Ccntniiculas, 

 Ammannia, Stiiija, Buimannici, small ScirpidecB, Campanulace(F, 

 parasitical Gentianea, and even some LegiiminofiCB, Selaginea, and 

 MeUistomacetB are enabled to exist solely through the instrumentality 

 of the Sci/tonemata which by night greedily absorb every dew-drop, 

 and thus preserve the roots of the little plants which they cover 

 from drying up by day under the influence of the burning tropical sun. 



Some large species of Batrachospernnun, all previously unde- 

 scribed, inhabit the streams of Pungo Andongo and Huilla, growing 

 in the former district in company with two species of Podostemoii. 



The red sea-weeds are more numerous than the brown, and 

 they are distributed among many genera ; a diminutive species of 

 Bostri/chia resides on the bark of Bhiwphoni Maiujle L., and with 

 its yellow-green colour clothes the trunks just like a moss, being 

 bathed with sea-water at high tide. UUilcnhiandtia is represented 

 by two species, one of which is new and abounds in the streams of 

 Golungo Alto, ornamenting the submerged rocks and stones with a 

 network of a blood-red colour. (See Welwitsch, Apont. 533.) 



A census of the collection of AlgiC, as determined by Miss IJarton 

 and the Messrs. West, respectively, shows 39 marine species in 

 32 genera, and 300 freshwater species in 77 genera; among the 

 latter 80 species occurred in the littoral districts of Angola or in 

 the African islands visited by Welwitsch, and 255 in the moun- 

 tainous districts or highland districts of Angola ; only one iiew 

 species of marine algre is described, but a large proportion of the 

 freshwater algna are new and contain lOG new species and 8 new 

 genera, two of the latter constituting new orders, namely, Tcmno- 



Journal of Botany, — Vol, 35. [Oct, 1897-] 2 u 



