660 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Production of Gummy Thyllae.* — In Ailanthus glandulosa, L. Mangin 

 finds an excretion of gum and the production of gummy thyllae, even 

 in trees which are in a healthy condition, and which have not in any 

 way been injured. They appear to result from a diminution of pressure, 

 produced during a certain period of the year, of the air in the trunk. 

 The cause of their frequency in injured or unhealthy trees is probably 

 a rarefaction of the air in the vessels, resulting from an insufficient 

 production of rootlets and a consequent diminution of the required 

 current of water to the leaves. 



Persistence of Leaf- traces, f — Sir W. T. Thiselton-Dyer records 

 several examples, in recent and fossil plants belonging to the Coniferae, 

 of the leaf-traces being continued to the leaves, where they are more or 

 less persistent, through several successive zones of wood. All the recent 

 instances observed belong to Araucaria. 



Apex of the Axis in the Flower of Gamopetalae.l — L. Vidal dis- 

 cusses the question whether, in the Gamopetalse, the axis takes part in 

 the constitution of the pistil or merely acts as a support to the carpel- 

 lary leaves. While the axis may assume very different forms in 

 members of the same family, the author concludes that, in the majority 

 of the Gamopetalee, it takes a more or less important part in the forma- 

 tion of the gynaaceum. In the most highly developed orders, the 

 Composite and Dipsacacese, the summit of the axis has usurped the 

 function of the carpel, the true carpel being reduced to nothing but the 

 style. 



Bark of Robinia Pseudacacia.§ — Pierre E. F. Perredes gives a 

 minute account of the structure of the bark of the locust-tree or false 

 acacia. 



Dr. F. B. Power || contributes an examination of the contents of the 

 bark. The toxic principle — robin or robinin — appears to be a true 

 proteid, probably belonging to the class of nucleo-proteids. It differs 

 from both albumoses and globulins in being soluble in water. It is 

 apparently an enzyme closely related to myrosin. Its chemical re- 

 actions and its physiological action are described in detail. 



Formation of Annual Rings in Tropical Trees.lf — A. Ursprung has 

 investigated the phenomena of periodicity in eight species of trees natives 

 of the Seychelles. He finds that, although there is in most cases a 

 connection between the periodicity of the formation of leaves and flowers, 

 and that of the increase in girth of the stem ; yet there are instances of 

 tropical trees which are deciduous and bloom periodically, but are 

 without annual rings in the wood ; and on the other hand, there are 

 species which are evergreen, and bloom all the year round, aud yet 

 form annual rings. The periodicity in the energy of the cambium 



* Comptes Eendus, cxxxiii. (1901) pp. 305-7. 



t Ann. of Bot., xv. (1901) pp. 423-5 (1 pi.). 



X Rech. s. 1. somniet de l'axe d. 1. flore d. Gamope'tales, Grenoble, 115 pp., 4 pis., 

 and 18 figs. See Bot. Centralbl., Ixxxvii. (1901) p. 93. 



§ Anatomy of tbe Bark of Robinia Pseudacacia. London, 11 pp. and 4 pis. 



|| Chemistry of the Bark of Robinia Pseudacacia, Loudon, 23 pp. 



*j Beitr. z. Anat. u. Jahresringbildung tropischer Holzarten, Basel, 1900, 81 pp. 

 See Bot. Zrg., lis. (1901) 2 U Abt., p. 229. 



