346 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Metamorphosis of Shoots.* — Herr M. Raciborski discusses the con- 

 ditions under which, in species with heteromorpbic branches (Langtriebe 

 and Kurztriebe), one kind may be made to replace tbe other kind. As 

 a general rule, decapitation incites the lateral buds to form branches of 

 tbe former kind ; while a transformation in the opposite direction is 

 the result of depriving a climbing stem of any support round which it 

 can twine. 



Theory of the Displacement of Lateral Organs by Mutual Pres- 

 sure. t — From observations of the cones of several conifers and the 

 capitules of Chrysanthemum Leucanthemum, Herr L. Jost disputes 

 Schwendener's theory that, in the course of the development of the 

 plant, young lateral organs may shift their place on the main axis 

 owing to displacements from mutual pressure. He finds the organs 

 always to retain the same position in relation to one another ; the 

 elongation of the axis takes place in such a way that all the individual 

 points move in lines parallel to one another and to the direction of 

 growth. 



Alteration of Phyllotaxis in Ascending Shoots.! — Herr A. Weisse 

 has made further observations on the effect produced on the arrangement 

 of the leaves by decapitation of the shoot. He finds that, in the case 

 of the hazel, the bilinear phyllotaxis is very readily changed into a 

 spiral one ; while this alteration is effected only in a few instances in 

 Tilia platyphyllos, and not at all in Vlmus campestris. In trees or 

 shrubs with a decussate phyllotaxis — Syringa, Acer, Fraxinus, JEsculus 

 — it is not uncommon for a threc-membered verticillate arrangement 

 to result ; less often a change to a spiral phyllotaxis. 



"Fore-runner Point" of Leaves.§— By this term (Vorlauferspitze) 

 Herr M. Raciborski designates a form of leaf-apex especially common 

 with tropical leaves, in which a region near the apex becomes well- 

 developed, and performs all the functions of assimilation, before the 

 basal portion of the leaf has attained any considerable development. 

 This suppression of the development of the greater part of the lamina 

 is especially displayed in those orders — Menispermaceae, Malpighiaceae, 

 Combretaceae, &c. — in which the young ascending shoots are at first 

 comparatively bare of leaves and possess an exceptionally strong cir- 

 cumnutation. This " fore-runner point " of the leaves closely resembles 

 the draining-point described by Stahl,|| but differs from that structure 

 entirely, both in its function and in its development. Very good 

 examples are also furnished by tropical Apocynaceaa and Asclepiadeae. 

 The same function is in some instances performed by the early forma- 

 tion of stipules. 



Aruncoid Leaves.^ — Herr R. Anheisser applies this term to the form 

 of leaf or leaflet of which that of Spiraea Aruncus may be taken as the 

 type. They have a lanceolate or ovate form, and are moderately apicu- 

 late ; they are almost always opposite ; the stomates occur on the under 



* Flora, lxxxviii. (1900) pp. 28-37 (7 figs.). 



t Bot. Ztg., Ivii. (1899) V Abth., pp. 193-226 (1 pi.). 



J Ber. Deutsch. Bot. Gesell., xvii. (1899) pp. 343-78 (1 pi.). 



§ Flora, lxxxvii. (1900) pp. 1-25 (8 figs.). 



|j Of. this Journal, 1894, p. 82. 



i Flora, lxxxvii. (1900) pp. t>4-94 (1 pi.) 



