1026 SUMMARY OF CURKENT RESEARCHES RELATING TO 



position and various form of the leaves in tlie upper part of older 

 trees is an attempt to adapt themselves to new conditions, when the 

 intensity of the sun's rays is above the optimum for the species, by 

 greatly diminishing the surface of leaf exposed to the direct action of 

 sunlight. 



Cecidomjda-galls on Poa.* — Herr W. Beyerinck has examined 

 the structure of the remarkable galls produced on the internodes of 

 the stem of Poa nemoralis by the attacks of Cecidomyia Poce. While, 

 under normal conditions, grasses are able to produce roots only from 

 the nodes, these galls are clothed with a thick matting of roots pro- 

 duced from the pericambial layer of the internodes. When first 

 formed these roots differ in no respect from ordinary underground 

 roots, being provided with a root-cap, and a central vascular cylinder 

 with a few pitted vessels, but with no root-hairs. In the course of 

 development they assume more and more the character of aerial roots, 

 and lose their root-cap. 



Opening of the Flowers of Desmodium sessilifolium.f — Prof. 

 C. E. Bessey describes the opening of the flowers of Desmodium 

 sessilifoUum ; the principal phenomenon connected with this being 

 that the resistance offered by the sepals is such as to cause the wings 

 and keel, with their inclosed stamens and pistil, to be strongly de- 

 flexed. The stamens and pistil are thus drawn downward as one 

 might draw down the end of a stiff spring. On pushing the standard 

 gently back by a touch with a pencil point near the vicinity of the 

 two bright yellowish-white eye-like spots on its dark-coloured base, 

 the stamens and pistil are freed with a violent jerk. The object of 

 this mechanism is obviously to cause the pollen to be thrown forcibly 

 against the body of any insect hovering over the flower or resting 

 upon its wings and keel. 



Inflorescence of Cuscuta glomerata.J — In his studies of this 

 degraded member of the Convolvulacese, Prof. C. E. Bessey has found 

 that the dodder produces its flowers upon short, adventitious branches, 

 which themselves repeatedly branch, and are closely covered with 

 scales. A further examination shows that this is the universal rule 

 with the species, no normal inflorescence developing. The adventitious 

 inflorescence always bears a definite relation to the position of the 

 parasitic roots ; that portion of the stem which produces roots always 

 produces flowers ; and the greater the number of the former, the larger 

 is the number of the latter. The stem proper dies away soon, not 

 only between the inflorescences, but also in the flower-clusters them- 

 selves. The flowering branches establish direct structural connection 

 with the host-plant. When this is accomplished, the scales upon the 

 branches often contain considerable quantities of chlorophyll. 



Relation of Ovary and Perianth in the development of Dicoty- 

 ledons.§ — Prof. J. M. Coulter describes a simple and important 



* Bot. Ztg., xliii. (1885) pp. 305-15, 321-32 (1 pi.). 



t Amer. Natural., xix. (1885) pp. 711-3 (4 tigs.). 



j Science, vi. (1885) pp. 225-6. (Proc. Sect, of Biology, Amer. Assoc. Adv. Sci. ) 



§ Bot. Gazette, x. (1885) pp. 360-3. 



