Schizothrix] xx. vaginarieje (West). 375 



dissepiments, and in the cells never being shorter than the diameter, 

 as well as in its subsolitary free-swimming habit. 



2. PORPHYROSIPHON Kiitz. (1850-52). 



1. P. Notarisii Kiitz. Tab. Phyc. ii. (1850-2), 7, t. 27, f. i.; W. 

 et G. S. West, in Journ. Bot. 1897, p. 271. 



This interesting and characteristic alga appears to have been 

 abundant in the district traversed by Welwitsch. 



PuNGO Andongo. — Alga terrestris, latissimas palustrium terrarum 

 plagas colore sanguineo-ferrugineo tingens, prope Oondo ; March 1857. 

 No. 9. Alga caespitosa, glauco-viridis, inter muscorum cseapites in 

 cryptis editiorum mentis de Cazella crescens ; Dec. 1856. No. 107- 

 (These specimens appear to be old ones ; many of the sheaths were 

 empty, and the red colour has mostly disappeared.) 



HuiLLA. — In udis sylvaticis et apricis inter Monino et lac. Ivantala 

 latas plagas colore fusco-sanguineo obducens ; April 1860. No. 14. 

 Frequens in pascuis pluv. autumnalibus frequentius inundatis, demum 

 exsiccantibus, ad lacum magnum de Ivantala ; March 1860. Nos. 17 

 and 18. "Alga terrestris, atro- vel fusco-sanguinea, late caespitosa, 

 csespitibus lubricis planis e fllamentis tenacibus dense intertextis et 

 contextis versus marginem radiantibus conflatis, terrse arete adhaerenti- 

 bus ; loca, ubi frequens obvia hsec Alga, tempore spongiosa facta multis- 

 aliis stirpibus uliginosis solum prsebent." 



This Alga occasionally branches ; these branches are few and of the 

 same thickness as the primary filament, around which they are closely 

 coiled. The sheath of the branch becomes solid at the base, and is 

 gradually merged into that of the primary filament, its trichome not 

 being in any way connected with that of the latter. The branching 

 really consists of a close application of the base of one filament to the 

 sheath of another, the fusion being for such a short distance that the 

 two trichomes are never present within the same sheath. It is of 

 the same type as the branching present in Schizothrix, but the division 

 into branches is deeper, causing the branches and primary filaments to 

 be of equal thickness. The above remarks prove that Porphyroaiphon 

 is very closely related to Schisoihrix, and emphasizes its position in the 

 Vaginariece. This affinity was inferred by Gomont (in Ann. Sci. Nat. 

 7° s^rie, Bot. xv. 332) from a consideration of an entirely different 

 character, viz. the structure of the sheath. Gomont's statement on the 

 same page that Porphyrosiphon has no branches is, however, erroneous. 



3. POLYCHLAMYDUM W. et G. S. West in Journ. Bot. 1897, 

 p. 271. 



1. P. insigne W. etG. S. West in Journ. Bot. 1897, p. 271, t. 365, 

 f. 1, 2. 



LoANDA. — Ad Nitellam et Najadem in lacu de Quifandongo ; 

 Dec. 1853. No. 195. 



The peculiar sheaths of this genus readily distinguish it from the 

 other genera of the Vaginariece, its nearest ally being Dasygloea Thw., 

 from which it differs ia the very firm multitubular sheath with an 

 open apex, and in the much thicker trichomes with very much shorter 

 cells. There is a very distinct line of demarcation between the inner 

 and outer constituents of the sheath, the outermost one being rendered 

 conspicuous only by the extraneous material adhering to it. The 

 trichomes are also usually without any interruption for a considerable 

 length. 



