374 SCIENCE PROGRESS 



soluble substance which inhibited germination. The water- 

 extract of a sample of similar soil was found likewise to inhibit 

 germination, but that it did not exercise any toxic effect upon 

 the seeds was proved by the fact that they germinated readily 

 after they had been rinsed thoroughly with water. 



The dormancy or delayed germination which is exhibited 

 by the seeds of certain plants when sown in an immature 

 condition immediately after removal from the parent plant 

 has been dealt with by F. Kidd and C. West (" The Role of the 

 Seed-coat in Relation to the Germination of Immature Seed," 

 Ann. Bot., xxxiv, 1920, p. 439), who, working with unripe seeds 

 of Brassica alba and Pisum sativum, have shown that the 

 removal of the testa not only accelerated the germination 

 and terminated the dormant condition of these seeds, but also 

 increased the germination percentage. These authors have 

 suggested that the rest period observed, when attempts are 

 made to germinate immature seeds immediately after removal 

 from the parent plant, may in many cases be attributed to the 

 presence of the testa, there being strong indications that under 

 these conditions the living testa limits the gaseous exchange of 

 the embryo. In this connection it is interesting to note that 

 C. H. Bailey (" Respiration of Shelled Corn," Univ. Minnesota 

 Exper. Stat. Techn. Bull., No. 3, September 1921) remarks 

 {I.e., p. 39) that " during the curing of corn on the cob immedi- 

 ately after harvest the rate of respiration is lower for a time 

 than that of corn of the same moisture content later in the 

 season." Bailey puts forward the view that " possibly a form 

 of dormancy is involved, resulting from a reduced rate of 

 diffusion of ox3^gen into the respiring cells, or of carbon dioxide 

 therefrom, or both." Moreover, according to H. Sherman 

 (" Respiration of Dormant Seeds," Bot. Gaz., Ixxii, 1921, 

 p. i), the data obtained in the course of a detailed study of 

 dormant seeds of Cratcegus seem to indicate that the respiratory 

 quotient and the rate of respiration are higher in the case of 

 the after-ripened seed than in the case of the dormant seed. 



J. S. McHargue (" Some Points of Interest concerning the 

 Cocklebur and its Seeds," Ecology, ii, 1921, p. iio) points out 

 that the dormancy which has hitherto been attributed to the 

 smaller of the pair of seeds borne in the bur of Xanthium 

 commune is only apparent, not real. The apparent dormancy of 

 the smaller seed is shown to be due, not to the exclusion of 

 oxygen by the seed coat as was indicated by the earlier 

 investigations of Shull (" Oxygen Pressure and the Germina- 

 tion of A^aw^^mm Seeds," Bot. Gaz., xlviii, 1909, p. 387), but 

 to the mechanical conditions within the bur, the chemical 

 composition and cell structure of the two seeds being similar. 



W. A. Gardner (" Effect of Light on Germination of Light- 



