Floristik, Geographie, Ss^stematik etc. 173 



der Kiefer nach Schweden kam. Durch das Auftreten der Fichte 

 litt die Art in ihrer Verbreitung grossen Abbruch. Vermehrte Kultur 

 in den norrländischen Flusstälern nebst fortgehender Erhebung des 

 Landes hat jedoch einigermassen diese Verluste ersetzt und neue 

 Standorte geschaffen. Mulgednim sibiricum ist daher als eine Folge- 

 pflanze zu Pffitts silvestris var. lapponica zu betrachten. 



Rob. E. Fries. 



Hill, A. W., Notes on Sebaea and Exochaennini. (Bull. Mise. Inf. 

 Roy. Bot. Cards. Kew. p. 317—341. 1 pl. 1908.) 



The genus Sebaea contains about 100 species of which some 

 belong to South Africa. These latter form the subject of the paper. 

 A key to the groups is given and new species are described and 

 some notes on other species are given. The foUowing are the new 

 species and varieties published: Sebaea {Tetraiidria) glaiica, A. W. 

 Hill, 5. aurea, R. Br. var. alata, A. W. Hill. Sebaea {Pentandria) 

 compacta, A. W. Hill, 5. conspiciia, A. W. Hill, 5. rotundifolia , 

 A. W. Hill, 5. prinniUna, A. W. Hill, 5. acuminata, A. W. Hill, 

 5. erecta, A. W. Hill, 5. imbricata, A. W. Hill, S. hymeno&epala, 

 Gilg, var. grandißora , A. W. Hill. 5. fastigiata, A. W. Hill, S. pro- 

 ciimbe)is, A. W. Hill. The old genus Belmontia, C. Me^^ is marged in 

 Sebaea. The genus Exochaeniiim has some of the species with di- 

 morphic flowers viz. E. grande, E. macranthuin and E. primtilaeßorum , 

 E. niacranthiini, A. W. Hill is described as a new species and E. 

 grande, Griseb. var. honiostylum , A. W. Hill as a new variety. The 

 plant formerly known as E. tnechowiammt has been referred to 

 Tachiadeniis. The paper is illustrated by a plate shewing the forms 

 of flower in several species of Exochaeniwn. A. W. Hill (Kew). 



Olsson-Seffer, P., Hvdrodynamic Factors influencing plant- 

 life on Sandy Shores. (New Phytol. VIII. 2. p. 37—51. 1909.) 



The author has made observations in many parts of Europe, 

 America, Australasia, etc. A "hj^'drodynamic-factor" is his expres- 

 sion to signity the influence of water in the soil upon plant-life as 

 distinct from edaphic and atmospheric influences. In the case of 

 sand, the amount of water held by the sand and its availabity for 

 plants determine the Vegetation , but in addition the presence of 

 soil-moisture checks drifting. Percolation of water through sand is 

 discussed from the experiments of Wiley, King and Seelheim. 

 Some experiments on capillarity attained in tubes of sand with 

 grains of known size are given and confirm the results of Klenze. 

 In "Western Australia, the author determined in a well in sand 

 97 m. from high water, that the water in the well stood at average 

 high tide 23 cm. above sea-level, and that minute fluctuations occur- 

 red traceable to atmospheric conditions and tidal oscillations. 

 Measurements of evaporation were taken on a dune (4.3 m. distant) 

 where it was found that moisture diminished up to 7.4 m. from the 

 ground-water-level, then it increased up to 68 cm. from the surface, 

 then diminished to the surface The observations made did not seem 

 to be fully explained by known factors — laws of ground-water- 

 level, capillarit}', and surface tension — , nor was the rainfall sufifi- 

 cient (2.17 cm. in 5 months). The author suggests "an internal dew 

 formation in the soil", due to condensation of water vapour with 

 anj^ periodic cooling — annual , nocturnal, etc. The effects of salts 

 on movements of soil water, the evaporation, and the effect of the 



