240 MORPHOLOGY, ETC., VASC. PLANTS [BoT. Absts., Vol. IX, 



fact as well as their conclusions and supporting the original theory. Special care is taken to 

 advance evidence that the large rays in many herbs are subtended by leaf-trace bundles since 

 a statement that this condition is rarely found constituted the chief criticism of the theory. 

 A comparison in regard to ray conditions is made between nearly related trees and herbs in a 

 wide variety of natural groups, including Malvales, Urticales, Ranales, Leguminosae, Scrophu- 

 lariaceae, and Compositae. From the facts brought out it is concluded that a practically 

 never-failing distinction between trees and the aerial axes of woody herbs is the formation in 

 the latter of large rays about the incoming leaf-traces, these rays being well-developed radially 

 but only slightly extended vertically. In less woody herbs the foliar rays become reduced 

 radially because of the thinning of the woody cylinder but at the same time become elongated 

 vertically. The vertical extension results in the division of the cylinder into a series of separate 

 strands. Finally, in the extreme herbaceous condition the woody cylinder is thinned to such a 

 degree that the radial extension of the foliar rays is eliminated. This condition is associated 

 with a great development of those portions of the ray on each side of the leaf-trace. — W. P. 

 Thompson. 



1492. Maillefer, Arthur. Les mouvements hygroscopiques des rameairs de rombelle 

 de Daucus Carota L. [Hygroscopic movement in the branches of the umbel of Daucus Carota.] 

 Bull. Soc. Vaudoise Sci. Nat. 52: 385-394. Fig. 1-10. 1919.— The hygroscopic effect, as mani- 

 fested in bending, was found to be greater in the distal than in the proximal half of the branches 

 of the umbel. In the proximal portion the vascular system is represented by numerous fibro- 

 vascular bundles of highly lignified, obliquely pitted elements, the bundles united into a cylin- 

 drical structure by masses of fibers with little dorsiventral differentiation. The distal part is 

 dorsiventral in structure. On the upper adaxial side is an arch of 4 vascular bundles, the 2 

 uppermost obliquely pitted, the 2 lateral ones transversely. As the latter are capableof greater 

 elongation, a mechanical differentiation is brought about between lateral and uppermost bun- 

 dles, which causes the movements observed. The bundle on the lower side tends to oppose 

 movement, but is not large enough to prevent it. By observing the action of longitudinal 

 sectors of branches, the author obtained evidence that Kleins' view (that movement is due to 

 difference in activity between abaxial and adaxial bundles) is erroneous. There is a marked 

 degree of dorsiventral differentiation with respect to presence of sclerenchyma. Martel is 

 wrong in assigning a major mechanical role to this, however, although it may be effective in 

 the nyctitropic movements occurring before the ripening of the fruit. — Charles Drechsler. 



1493. Maillefer, Arthur. Sur le d^veloppement de la structure anatomique de la tige 

 d'Impatiens Roylei Walpers. [Development of the anatomical structure of the stem of Impatiens 

 Roylei Walpers.] Bull. Soc. Vaudoise Sci. Nat. 52: 237-274. Fig. 1-27. 1919.— The young 

 hypocotyl of this species shows 4 strands of protoxylem between each 2 of which may be dis- 

 tinguished 2 groups of phloem elements. The epidermis, a single layer of cells, overlies a 

 layer of collenchyma cells which is separated from the endodermis by a thick cortex. Metaxy- 

 lem cells begin to appear on the inner side of the protoxylem groups, which gradually disap- 

 pear. The phloem now increases in mass and the cambium begins to appear and forms second- 

 ary wood near the lateral edges of the primary wood, A cavity results from the degeneration 

 of the central portion of the pith. The secondary wood cells gradually assume isolated posi- 

 tions toward the center of the stem. The mature hypocotyl shows a layer several cells thick 

 immediately inside the endodermis, the pseudopericycle. The cambium ceases to function 

 after forming a considerable layer of fibers and vessels. Secondary parenchyma rays are pres- 

 ent, distinct from medullary rays and having no relation to the pith. — The development of the 

 stem is followed in the same way. In mid-summer a longitudinal section shows the tissues in 

 the following order: Epidermis, dermal collenchyma, cortical cells, endodermis, phloem, 

 cambium, pitted vessels, woody fibers, collenchymatous woody parenchyma, scalariform ves- 

 sels, spiral vessels, and pith. Short sections are devoted to the structure of the phloem, the 

 course of the vessels, the structure of adventitious roots, and the distribution of anthocyan 

 in the epidermis. — Charles Drechsler. 



