622 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



extent by hydrogen and nitrogen. They become brownish and 

 acquire a bad flavour when oxygen is withheld from them. Ice- 

 scald " seems to be due to insufficient oxygen and to an accumulation 

 of carbon dioxide within the paper wrappers in which peaches are 

 often packed. Good ventilation in conjunction with refrigeration is 

 of prime importance for the successful storage of fruit. — F. J. C. 



Germination, Delay in. By WiUiam Crocker and Wilmer E. 

 Davis {Bot. Gaz. Iviii. pp. 285-321, October 1914 ; 8 figs.). — The 

 authors point out that the germination of seeds is delayed by exclu- 

 sion of water as in " hard-seeded " legumes, &c., by the envelopes sur- 

 rounding the embryo, which prevent swelling, as in A lisma and other 

 water plants, or which exclude oxygen, as in some Compositae, and 

 perhaps by a deficiency in nutritive salts. The slow development 

 of acid delays development of the embryo in some Rosaceae. 



Some embryos, however, remain dormant even when all coats are 

 removed. 



The seeds of ^/zsm^j, with which the authors experimented, remain 

 in water for years without germinating, but an air-dry seed when 

 freed of the envelopes increases 40 per cent, of its weight in two hours, 

 and slowly afterwards to 50 per cent. When partly swollen and 

 still within the coats, it probably exerts a pressure of 100 atmospheres 

 against the seed-coat. 



When the coat-cap is removed from the embryo, the latter swells 

 even more rapidly (60 per cent, more in two hours and 100 per cent, 

 after 20 hours). The imbibitional force of the embryo is increased 

 greatly by bases and very slightly by acids. These probably affect 

 germination by weakening the seed-coats, though they may also affect 

 osmosis. 



At the expense of its stored food only, the embryo of Alisma is 

 capable of an elongation of 120 per cent, in total absence of oxygen. 

 To become green at least 5 mm. of air pressure is necessary, and more 

 than 5 cm. to produce branching or to develop primary roots. 



Seeds of land plants cannot usually survive for more than a short 

 time when lying in water. — G. F. S. E. 



Germination of Avena fatua. By W. M. Atwood {Bot. Gaz. 

 Ivii. pp. 386-414, May 1914 ; 13 figs.). — ^The exact nature of the 

 changes which result in after-ripening of the seed cannot be given 

 positively. But the acid contents of the embryo and its permea- 

 bility to water are increased, resulting in increased water-absorbing 

 power. 



Both shell-coats and seed-coats interfere with oxygen supply. 

 The results of the author's experiments obtained by breaking and 

 searing the seed-coats, by removal of the embryo, by varying con- 

 centrations of oxygen, and by direct measurement of the rate of 

 oxygen intake with intact and seared seeds seem to show that the 

 limiting factor to germination is probably a restriction in the supply 

 of oxygen. 



