320 EXPERIMENT STATION EECORD. 



It was foniKl that during the first 24 to 48 hours 2 seedling plants when 

 grown together often promote the growth of each other, but afterwards bacteria 

 and aquatic fungi prey upon the dead cells of the root cap, and upon the dying 

 root hairs, producing substances decidedly injurious to the roots. 



The injurious effects noted are attributed mainly to the excretion of fungi 

 and bacteria in cultures. It was found that when a plant was watered with 

 plant juice the first bacteria or fungi which attacked the plant juice produced 

 harmful effects, and it was not until these harmful excretions were decomposed 

 by other bacteria or by the chemical action set up by manure that the injurious 

 causes were removed. The excretion of fungi was usually injurious to plant 

 roots, excepting in the case of a symbiosis of mycorrhiza and host. Prelim- 

 inary experiments indicate, however, that the excretion of mycorrhiza is in- 

 jurious only to the roots of other than those of the host plant. 



In conclusion the author says that the loose cells set free by roots are the 

 prime cause of the injury, though not the direct cause. They furnish food for 

 fungi and bacteria, but it is the excretion of these organisms that causes the 

 injury. 



[Studies on the adventitious embryos in the orange and mango], J. Bell- 

 ing (Florida Sta. Rpt. 190S, pp. C7.Y-C'A'-YT', pis. o). — Attention is called to 

 the work of Strasburger and others showing the occurrence of adventitious 

 embryos in. the seed of the orange, and the results of the author's investigations 

 with the mango are described at length. 



A large number of seeds of a variety known as No. 11 were examined and 

 comparisons made with other varieties. The occurrence of polyembryos seemed 

 to be quite constant in some of the varieties, while an examination of the egg 

 cells of fruits of the variety No. 11 from isolated trees showed that there was 

 no embryo formed in the embryo sac, all the embryos being ai)parently ad- 

 ventitious. Attention is called to the fact that mango seeds may retain their 

 vitality for a considerable time during the hot weather in Florida, and that 

 stones taken from mango fruits immediately upon gathering, if cleaned from 

 the pulp and planted in clean sand, usually give healthy germination. These 

 results confirm those of Higgins as reported in Bulletin 12 of the Hawaii 

 Station (E. S. R., 17, p. 1155). 



Further contributions to the subject of graft hybrids, H. Winkler (Ztschr. 

 Bat., 1 (1909),. No. 5, pp. SloS-'/o, pi. 1, figs. Jf). — In continuation of previous 

 reports on a graft hybrid between the cultivated tomato and the black night- 

 shade, further notes are given on this form, which the author has called Sola- 

 ntim tuhingcnsc, and descriptions of additional graft hybrids are given. These 

 new forins have been designated by the following names : S. protcus, S. darwin- 

 ianttm, S. koclreuteriamim, and S. gccrtnerimmm. 



Trees, H. M. Ward (Cambridge, 1909, vol. 5, pp. X+ 308, pi. 1, figs. 209).— 

 This volume treats of the form and habit of trees, with an appendix on seed- 

 lings, and is the concluding volume of the Handbook of Forest Botany for the 

 AVoodlands and the Laboratory. The previous volumes have already been 

 noted (E. S. R.. 20. p. 113.3). 



American medicinal barks, Alice Henkel (U. S. Dcpt. Agr., Bur. Plant 

 Indus. Bui. 139, pp. 59, figs. //J). — In this bulletin, which forms the second of a 

 series on American medicinal plants (E. S. R., 19, p. 529), are given descrip- 

 tions of the barks recognized as " official " in the eighth revision of the United 

 States Pharmacopoeia, together with a number of other " nonofiicial " ones that 

 are in considerable demand, if judged from the quotations and trade catalogues 

 of dealers in drugs. The number of drug plants fully described is 35, but under 

 many descriptions closely related species are also briefly treated. 



