NOTES AND ABSTRACTS. 



NOTES AND ABSTRACTS. 



After-Ripening and Germination of Seeds of Tilia, Sambucus, and Rubus, 



By R. C. Rose (Bot. Gaz. vol. lxvii., No. 4, April 1919, pp. 281-308). — "Air- 

 dry seeds of Tilia americana, Sambucus canadensis, and Rubus »Idaeus do not 

 germinate when placed in a moist substratum at room temperature. In no 

 case does water absorption seem to be the limiting factor. Air-dry seeds 

 planted in the soil over winter give low percentages of germination." 



In the case of Tilia, " seed coats are not the cause of dormancy, although they 

 may serve to lengthen the dormant period. A state of dormancy exists in the 

 endosperm or embryo, or both. 



" Seeds with coats removed after-ripen at temperatures slightly above freezing. 

 From o°-2° C. seeds after-ripen, but do not germinate. Above this temperature 

 both processes may occur. 



" With Sambucus as high as 77 per cent, of germination was obtained by 

 layering fresh seeds out of doors over winter, but no satisfactory forcing agent 

 has yet been found. 



" Dormancy in Rubus is probably due to the high breaking strength of the 

 endocarp. Seeds treated with concentrated sulphuric acid for two hours, then 

 thoroughly washed, germinate readily on cotton, filter paper, or quartz sand. 



" The optimum temperature for germination lies between 20 0 and 25 0 C. Seeds 

 germinate equally well in light or darkness. Naked seeds germinate poorly 

 in soil, probably on account of the action of bacteria and fungi." 



A practical method for the germination of Rubus seeds, apart from layering, 

 is described. This method is based upon the action of concentrated sulphuric 

 acid.— R. J. L. 



Amaranthus: Chemical Constituents of Amaranthus retroflexus. By M. L. 



Woo {Bot. Gaz. vol. lxviii. No. 5, Nov. 1919, pp. 313-344 ; with 11 figs.). — ■ 

 The investigations described in this paper were carried out primarily to find 

 whether Amaranthus stores nitrogen in the form of nitrates, as has been con- 

 tended. It is quite apparent that a weed would become a formidable rival of 

 cultivated plants by withdrawing the nitrogen from the soil. 



It was found that there is a large amount of nitrogen in Amaranthus, stored 

 principally in the stem and branches. " The rate of nitrate absorption increases 

 with the aging of the plant, perhaps being partly due to the development of 

 the root system, with numerous branching rootlets increasing the radius of the 

 feeding area from a few inches to two feet or more. 



" The carbohydrates and nitrogen compounds fluctuate throughout the 

 growing period. In general, when the carbohydrates are high, the nitrogen 

 compounds are low, and vice versa." — R. J. L. 



American Blight. By A. Magnien (Rev. Hort. vol. xci. p. 371). — To protect 

 fruit-trees from American blight, surround the stems with manure in October 

 and brush the affected parts with paraffin emulsion. 



Or spray with water at 8o° C. containing 1 per cent, nicotine and sodium 

 carbonate. — 5. E. W . 



Amylase, Secretion of Amylase by Plant Roots. By L. Knudson and R. S. 

 Smith (Bot. Gaz. vol. lxviii. No. 6, Dec. 1919, pp. 460-466 ; with 2 figs.). — 

 In culture experiments conducted with Zea Mays L. and Pisum arvense L., it 

 was found that the roots were unable to utilize soluble starch, and there was 

 no appreciable secretion of the enzyme amylase. — R. J. L. 



Aphis-feeding Ladybird (Bull. State Comm. Hort., California, viii. 2, Feb. 

 1919 ; 22 figs.). — Among other items of interest contained in this bulletin 

 is an account of the work of distributing colonies of the aphis-feeding ladybird 

 (Hippodamia convergens) to the farmers and fruit-growers of the State. During 

 the season about 75,000,000 of these insects were shipped from the insectary, 

 mainly to the Imperial Valley, for use of grain and cantaloupe growers. — V . G. J. 



