1132 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



The next stage is for the xylem to be filled with pith in the middle. 

 This is the tubular stele. 



The solenostele follows, in which a zone of phloem occurs in the 

 interior of the xylem as well as outside it. 



Now follows the solution of these three concentric rings into separate 

 steles, forming the diastclic or polystelic condition. From this we trace 

 the origin of the fibro-vascular bundles of Gymnosperms and Dicotyle- 

 dons. This is brought about by the arrest of the centripetal growth. 

 Having been a mesarch, i.e. growing both ways, the bundle becomes 

 endarch, or only grows centrifugally. — G. H. 



Yeast Proteolysis. 

 Yeast Enzymes Proteolytic {Belli. Bot. Cent. bd. xiii. ht. 2, 



pp. 235-264). — Professor Dr. Th. Bokorny records many experiments 

 showing that yeast can produce both peptic and tryptic enzymes. Under 

 certain conditions only peptones and propeptones are formed, but badly 

 nourished "Hunger" yeasts produce Tyrosin, Leucin, and Hexonbases. 

 Both animal and vegetable albumen can be proteolysed by yeast. The 

 experiments were conducted with " Flesh fodder meal" (Liebig's), Pease 

 meal, Soja Bean meal, and Rape seed. From 10 % to 40% dry or fresh 

 yeast was used, with 0*5 to 1 % phosphoric acid, at temperatures from 

 35°-40° (in one case 20°). The time permitted was generally 24 hours, 

 though in some cases 2 hours and in others 120 hours. The amount of 

 the albuminous material proteolysed was in one case 20 %, but in others 

 much less (from 1*5 to 2*8 % in most cases). The yeast proteolysis is 

 also compared with that produced by animal pepsin and trypsin, and 

 with acid proteolysis. A critical account is given of various researches 

 with regard to variations in the amount of enzyme produced. Protein 

 material appears to assist the formation of enzymes. The paper is of 

 great importance for students of yeast, and of fermentation generally. 



G. F. S.-E. 



