NOTES AND ABSTRACTS. 



151 



1908). — A short account is given of each of the various kinds of tropical 

 fruits which have recently been for sale in Covent Garden Market ; the 

 author says " it may be of interest to give a few particulars concerning 

 these, as well as descriptive notes from my own experience in the tropics." 

 The paper is a decidedly interesting one. — G. S. S. 



Tunica Saxifraga, Double. By G. T. Grignan (Bev. Hort., 

 December 1, 1908, pp. 543, 544 ; one illustration). — The illustration re- 

 presents a very pretty and floriferous specimen of this Saxifrage, evidently 

 well fitted for rockeries or pot culture. — C. T. D. 



Tyloses. By Hermann von Alten (Bot. ZeiU 67th Jah, Aug. 29, 

 1909, Heft 1, pp. 1-23, with 4 figures and 1 plate).— A very useful 

 summary and discussion of what is known with regard to tyloses. 

 An unknown writer in 1845 correctly explained them as protuberances 

 of the surrounding parenchyma cells into the cavities of the vessels. 

 They may be the result of reduced tissue tension in the vessels owing to 

 a wound, or to an abnormally low gas pressure caused in old wood by the 

 cessation of water conduction. They sometimes close up or seal the 

 vascular tissue, preventing loss of water, but in the case of climbing 

 plants they may assist in the ascent of sap by diminishing the width of 

 the vessels. Sometimes they act as ' pumps ' pressing out carbonic acid 

 into the sap and extracting from it nutritive salts. There is also a useful 

 bibliography. — G. H. S.-E. 



Weight, Measurements of, Increase in. (Beih. Bot. Ccntralbl, 



xxiv., Erste Abth., Heft 1, pp. 45 et seq ; with four figures.) — Dr. Hugo 

 Hackenberg gives a series of tables dealing with the rate of increase in dry 

 weight of Cannabis sativa and C. gigantea. The " substance quotient " 

 is obtained as follows : Specimens are taken at fixed intervals ; the 

 average dry weight at each period is then divided by that found at the 

 preceding time of measurement. 



The seedlings one week old were 3*3 to 6*7 per cent, lighter in dry 

 weight than the same number of seeds before planting. 



After this period there is an increase in dry weight, and the substance 

 quotient varies from 1*9 to 2*5. After the difference in sex is perceptible, 

 the male plants increase more slowly than the females. In some of the 

 male plants the weight was actually less after flowering (due to loss of 

 leaves and pollen). 



The quotient curves seem to be independent of normal climatic 

 fluctuations. The plants assimilated with the same regularity in spite of 

 unfavourable conditions. But when a series of both male and female 

 plants were grown in shade the quotients were distinctly lower in the 

 shaded plants, and the dry weight was very much smaller than in the 

 control sun -plants. 



The male plants were more injuriously affected by shade than the 

 female ones. — G. F. S.-E. 



Woburn, Ninth Report, 1908. By the Duke of Bedford, K.G., 

 and Spencer U. Pickering, F.R.S. — This Report deals mainly with ex- 

 periments in unorthodox methods of planting, and these have been 



