832 SUMMARY OF CURRENT RESEARCHES RELATING TO 



metres and micro-millimetres, as determined by different observers, 

 whoso initials are appended, and all the figures arc drawn to a 

 uniform scale of 400 diameters, except in a few instances whero further 

 enlargement is necessary. 



Formation of Auxospores in Rhizosolenia alata.* — Herr F. 

 Schiitt describes the formation of auxospores in this diatom which 

 occurs in great abundance in the Baltic. It multiplies by division in 

 the ordinary way in the spring and summer ; tho auxospores are 

 found chiefly in August and September, and differ greatly in appear- 

 ance from those of most diatoms, having heen described by previous 

 observers as distinct species or varieties. 



When an auxosporo is about to be formed, a slender mother-cell 

 breaks up into two half-frustules. Through tho opening thus formed 

 in one of the half-frustules tho protoplasm swells in tho form of a 

 capitulum, and excretes on the surface in contact with tho water a 

 silicified membrane which attaches itself to tho old girdle-band, and 

 thus becomes an auxosporo. Tho capitulum elongates into a short 

 cylinder, excretes on its inner side a shell, and thus becomes an 

 augment-cell. This may form in succession a number of daughter- 

 cells by the elongation and bipartition of the thick end ; tbeso are 

 unlike the augment-cell, and differ from the mother-cell only in 

 greater stoutness. The augment-cell itself may become transformed 

 into a daughter-cell after having undergone a larger or smaller 

 number of divisions. The daughter-cells are the starting-points of 

 new generations which increase further by bipartition. 



Fungi. 



Acrogenous Development of the Spores of Fungi.j — M. J. de 

 Soynes points out that the ordinary statement that the spores or 

 conidia of fungi are formed exogenously by simple cell-division is 

 not in all cases strictly correct. In a species of the genus Sporo- 

 chisma, found on over-ripe pineapples, the spores are formed dis- 

 tinctly within tho cell next lowest on the chain, from which they 

 escape through a small orifice formed in the wall at the apex of the 

 mother-cell. Spores which are ultimately developed acrogenously, 

 and are termed acrospores, are here distinctly originally of endogenous 

 origin. 



Germination of Spores of Ustilago Vaillantii.l — According to 

 Sig. F. Morini, when the spores of this fungus germinate in rain- 

 water, they put out short and but slightly branched germinating 

 tubes ; while in spring-water which contains mineral salts and organic 

 substances, they give out one long and branching tube from each pole. 

 In a drop of nutrient solution, such as a decoction of the flowers or 

 leaves of Bellevalia romana, the germinating spores form short simple 

 tubes, which multiply abundantly by budding ; these developc ovoid 



* Ber. Deutsch. Bot. Gesell., iv. (lSSG 1 ) pp. 8-14. 



t Comptes Rendus, xcii. (1886) pp. 933-4. Cf. this Journal, ante, p. 488. 

 X Mem. R. Accad. Sci. 1st. Bologna, vi. (1885) 9 pp. (1 pi). See But. 

 Centralbl., xxvi. (188G) p. 209. 



