534 Annals of the Smith African Museum. 



cells becomes more irregular ( Fig. 17, A). The chloroplast appears to 

 have but a single pyrenoid. 



This species stands near to the Stigeoclonium farctum of Berthold 

 (Unters ueb. d. Verzweig. einig. Suesswasseralg., Nova Acta K. Leop.- 

 Carol. Ak. d. Naturf., xl, No. 5, 1878, pp. 201, 202, Tab. II, figs. 1-5), 

 which, like our species, bears short bunched branches and irregularly 

 scattered hairs, arising from the highly developed creeping portion. 

 The principal differences are : (a) The radial method of branching of 

 the procumbent portion and the apparently customary formation of a 

 pseudo-parenchymatous disc; (b) the proportionally wider and 

 shorter cells of the creeping base ; (c) the longer and less pointed 

 vertical branches, which may in rare cases be branched ; and (<1) the 

 absence of a swelling at the base of the hairs. Berthold's description 

 also o-ives the impression that the development of upright branches is 

 much more abundant than in our form. The writer has described a 

 var. simplex of 8. farctum, Berthold (Obs. on the young plants of 

 Stig., Beih. Bot, Centralbl., xiii, 1903, p. 376 et seq., Tab. XI, figs. 1-14), 

 which is, however, more remote from our species than 8. farctum 



itself. 



Moebius (Ueb. einig. in Portorico gesamm. Suessw.-u. Luft.-Alg., 

 Hedwigia, xxvii, 1888, p. 239, Tab. IX, fig. 3) has described an 

 epiphytic species (without name) of Stigeoclonium, growing on leaves 

 of Potamogeton occidentalis • this is, however, much more like 8. 

 farctum than our species. 



Hansgirgs Stigeoclonium pygmaeum (Prodr. d.Algenfl.v. Boehmen 

 i, 1888, p. 69, fig. 28), which he subsequently (op. cit., ii, 1893, p. 217) 

 regarded as a variety of 8. farctum, appears as quite a different form, 

 and Heering (pp. cit., p. 85) is no doubt right in maintaining it as a 

 distinct species. Collin's 8. subs implex (The Green Algae of N. 

 Amer., Supph, Tuffs Coll. Studies, iii. No. 2, pp. 90-92, fig. 6) appears 

 to be closely allied to Hansgirg's species. 



Genus MICROTH AMNION Naegeli. 



1. Microthamniun strictissimum, Rabenhorst, Krypt, Flora v. 

 Sachsen, etc., 1863, p. 266 ; PI. Europ. Alg., etc., iii, 1868, p. 375. 



Samples 11,12, 13. 



2. Microthamnion kuetzingiamim, Naegeli, in Kuetzing, Spec. Alg., 

 1849, p. 352. 



Sample 36. 



