AGEICULTUEAL BOTANY. 521 



vestigations were continued to determine wlien the resting phase sets in and 

 whether It can be brolien by treatments and what agents are most effective 

 for brealiing the rest. 



During 1912 and 1913 a study was made of about 100,000 seeds representing 

 about 200 species of plants, and it was found that about 76 per cent had a 

 definite rest period. Where seeds grow at all without rest, germination takes 

 place more quickly in the immature seeds than in mature ones. 



In 1912 seeds of a number of species of woody plants were treated to break 

 the rest period. It was found that stratifying these seeds and letting them 

 freeze while in the moist sand proved the best treatment tried for hastening 

 the sprouting and bringing about the highest percentage of germination. 

 Etherizing dried or moist seeds had some beneficial efiiect on germination, 

 and etherizing seeds that had been stratified and frozen hastened sprouting 

 and also increased the percentage of germination. Etherizing old, dry seeds 

 of herbaceous plants had but little effect on germination and in most instances 

 was found detrimental. Seed coi*n etherized when dry seemed to be materially 

 benefited. It was found that while corn seed did withstand severe freezing 

 when dry it was badly injured when in a moist or wet condition. Lima beans 

 were found to be severely injured if frozen when dry, and proportionately 

 greater injury was effected if wet. Freezing and etherization were detri- 

 mental to watermelon seeds if dry, but they were not injured and in some 

 cases were benefited by freezing, if the seeds were quite moist. Soaking 

 okra seeds had a bad effect on germination, and ether treatments had little or 

 no effect on dry seeds, but were very beneficial to moist or wet ones. 



A historical summary and bibliography are appended. 



Experiments in forcing native plants to blossom during the winter 

 months, C. O. Rosendahl {Plant World, 11 (1914), No. 12, pp. 354-361).— 

 Giving an account of attempts to obtain fresh flowers for class use during the 

 winter months, the author states that while the experiments made were not 

 comprehensive enough to form a basis for sweeping conclusions, it has been 

 demonstrated that a considerable portion of the perennials native to the neigh- 

 borhood of Minneapolis, IMinn., lend themselves to successful forcing during 

 winter and that a wealth of fresh material can thus be obtained with compara- 

 tively little effort and expense. 



The effect of shade on transpiration and assimilation of tobacco in Cuba, 

 H. Hasselbking (Estac. Expt. Agron. Cuba Bol. 24 (1915), pp. 1-33, fig. 1). — 

 The principal conclusions from this work have already been noted ( E. S. R., 31, 

 p. 326). 



Absorption of ions by plants, F. Plate (Atti B. Accad. Lincei, Bend. CI. 

 Sci. Fis., Mat. e Nat., 5. ser., 23 (1914), -f. No. 10, pp. 839-844; a^s. in Jour. 

 Chem. Soc. [Londonl, 106 (1914), No. 622, I, p. 1039).—TrUicum sativum and 

 Hyacinthus 07-ientalis were grown separately in solutions of the chlorid, bromid, 

 nitrate, and sulphate of manganese. It was found that the anion and cation are 

 utilized in about the same proportion as that which obtains in the solution, the 

 anion going mainly to the shoot and the cation to the root. 



The antagonism between ions in the absorption of salts by plants, W. 

 Stiles and I. Jokgensen (New Phytol., 13 (1914), No. 8, pp. 253-268) .—The 

 authors review briefly the work and opinions of earlier investigators dealing 

 somewhat indirectly, and those of later ones dealing more directly, with antago- 

 nism between salts or ions in their absorption from aqueous solutions by plants. 



It is considered as evident that this phenomenon is of widespread if not of 

 universal occurrence in organic life. Antagonism appears to be characteristic 

 of cations, not only of nutritive but also of indifferent or poisonous character, 

 7700°— No. 6—15 3 



