GIC SUMMARY OF CUURENT RESEARCHES RELATING TO 



(5) Phenomena resulting from tUo positive hcliotropisni of tbo 

 specific protoplasm of the shoot: — Tlio positively heliotropic curvatures 

 of growing shoots; the fact that seedlings, when growing in the light 

 on a block of tiu'f rotating in a clinostat, place their hypocotylcdonary 

 organs at right-angles to the surface of the block. 



(6) Phenomena resulting from the negative hydrotropism of the 

 specific protoplasm of the shoot: — The negatively hydrotropic curvatures 

 at the conidiophore of Phi/comyccs niicns. 



(7) Phenomena which must be regarded as a consequence of a com- 

 bination of these various causes. 



Sensitive Labellum of Masdevallia muscosa.* — Mr. F. W. Oliver 

 states that up to the present time only two genuine cases of motile 

 labella have been recorded in Orchids : Megadimum, in which tho 

 movement is spontaneous, and Pterosfylis where it is called forth by an 

 external stimulus. The object of the present paper is to give an account 

 of the mechanism of movement of a new case, 3Iasdevallia muscosa Rchb. f. 

 This plant produces a number of flowers borne singly on erect scapes 

 some 15 cm. long. The labellum is roughly triangular and articulated 

 by a delicate hinge to the foot. The movement is displayed as a sudden 

 and rapid folding up of the labellum on its band-like neck, so that tho 

 broad distal part of the blade is approximated to the top of the column. 

 This movement is called forth by the gentlest touch of a hair or insect's 

 foot on the median crest of the blade. Within a second of stimulating 

 the crest, the blade is moved upwards through an angle of some 10'^, 

 then for a brief space, which is only just appreciable, and amounts to 

 a small fi'action of a second, a slight hesitation or slowing, as it were, 

 is noticeable, and finally, the upward movement is continued through 

 a further angle of 70' or 80° with groat rapidity. The whole process 

 barely occupies two seconds. This manifestation of movement in tho 

 labellum seems to bo simply one of the numerous ways chanced on 

 by orchids in promoting cross-fertilization by the agency of insects. 



(4) Chemical Cliang^s (including' Respiration and Fermentation"). 



Formation of Nitric Acid in Plants.f — Ilerr B. Frank contests tho 

 ordinary view that the conversion of niti'ates into organic nitrogenous 

 substances takes place exclusively in the leaves. He finds, on tho 

 contrary, as the result of direct experiments, that in those which he 

 terms " nitric acid plants " much more nitric acid is absorbed during 

 the period of growth than is required at the time for the formation of 

 new organs, and that the excess accumulates in the form of unchanged 

 nitrates in all the organs adapted for the purpose — the parenchyma of 

 the root and stem, the leaf-stalk, and veins — where it is stored until tlie 

 period of ripening of the fruit. The transformation of the nitrates into 

 nitrogenous substances which serve as food-materials for the plant takes 

 place in all the organs which are penetrated by vascular bundles, even 

 in the root. Ho further states that the whole of the nitrate contained 

 in vegetable tissues must have been absorbed as such by the root, the 

 plant having no power, whether in the light or in the dark, of converting 

 ammonium salts into nitrates. 



As examples of typical " nitric acid plants " Herr Frank names the 



» Ami. of Bot., i. (18SS) pp. 2.^7-53 (1 pi.). 



t Ber. Deutsch. Bot. Gesell., v. (1887) pp. 472-87. 



