ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 243 



adult petiole, a central fibrovascular arc will be found, and between the 

 extremities of this arc and the wing, both to right and to left, will be 

 seen three or four fibrovascular bundles. By a most cursory observa- 

 tion it will be seen that these lateral fibrovascular bundles are exactly 

 parallel to the foliar bundle, and longitudinal sections will show that 

 there is no communication between the different bundles of the petiole. 

 Finally it will be seen that each of these lateral bundles possesses a 

 simple and complete pericyclic layer. The author then traces the 

 formation of these lateral bundles which he states are formed at the 

 expense of the parenchyme of the wings of the petiole. 



Vascular Bundles in the Rhizome of Monocotyledons.* — Herr 



W. Laux gives the following as the general results of his investigations 

 on this subject. The concentric or perixylematic bundles of the rhizome 

 are not distinguished from the collateral bundles of the leaf and stem 

 by the nature of their elementary constituents, but only by the relative 

 position of the xylem and phloem. The passage from a collateral to a 

 concentric bundle usually takes place by the xylem enveloping the 

 phloem in one and the same bundle ; and the transition from one to the 

 other is usually very gradual. One and the same collateral bundle may 

 be first transformed into the concentric and then back into the collateral 

 type ; this has been observed in the nodes of Juncacese. In one and the 

 same transverse section all stages of transition may be seen from the 

 collateral to the concentric type ; the collateral bundles belonging to 

 older, the concentric to the younger leaves. 



As regards the arrangement of the bundles in the rhizome, this is 

 nearly uniform in the genus Juncus, while in Carex it displays the 

 greatest variation, arranged under as many as nine different types, if the 

 structure of the cortex is taken into account. A connection in general 

 terms was observed between the arrangement under these different types 

 and the nature of the habitat of the species. Those species which 

 exhibit large lacunas in the fundamental tissue, especially in the cortical 

 parenchyme, inhabit moist localities ; whilst those which grow in dry 

 situations, as on grass-plots, have their fundamental tissue more solid. 

 Both collateral and concentric bundles occur in the same genus. 



Bacillar Tumour on Pinus halepensis.f — M. P. Vuillemin describes 

 the structure of a bacterian gall found on Pinus halepensis. In the 

 cavity which was found on making a section was an accumulation of 

 immotile bacilli which were feebly stained by anilin. In the hyper- 

 trophied parenchyme were woody irregular nuclei having circular or 

 sinuous outlines. A more complete dissection, combined with the 

 examination of young material, showed that these hard corpuscles were 

 connected with each other, and that they were expansions of a ligneous 

 mass dependent on the normal wood of the stem. 



Mechanical Structure of Floating-Organs. | — Dr. H. Dingier de- 

 scribes the various mechanical contrivances by means of which fruits and 

 seeds are enabled to float in the air, classifying them under twelve heads. 

 Excessively slow deposition in the air is secured in some cases by the 



* Verhandl. Bot. Ver. Prov. Brandenburg, xxix. (1888) pp. 65-111 (2 pla. and 

 1 fig.)- 



t Comptes Reudus, cvii. (1888) pp. 874-6. 



t SB. Bot. Vereins Munchen, April 23, 1888. See Bot. Centralbl., xxxvi. (1888) 

 p. 386. 



