ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 71 



leaf, so as to divide it more or less completely into several palisade- 

 like cells. This structure was observed in many Eanunculacese, as 

 Anemone, Caltha, Trollius, Pceonia, Aconitum, and Clematis ; in Sam- 

 bucus ; among Monocotyledones in Alsircemeria ; and in some grasses, as 

 JElymus, Bambusa, and Arundinaria ; in Pinus ; and in the fronds of 

 Adiantum and Dodea. The function does not appear to differ from 

 that of the ordinary palisade-tissue. 



Formation of Healing-tissue and Fall of the Leaf.* — In an 

 exhaustive treatise on the nature of the tissue formed to protect 

 wounds in the process of healing, and on the phenomena connected 

 with the fall of the leaf, Freiherr v. Bretfeld distinguishes the three 

 following different modes of healing, characteristic of different plants : 

 — (1) By the drying up of the surface of the wound ; (2) by the 

 formation of periderm ; (3) by the formation of reticulately thickened 

 cells. 



Membrane of Bordered Pits.f — J. Moeller returns to the contro- 

 versy respecting the true explanation of the appearances presented 

 by bordered pits. He dissents from von Hohnel's view, that the so- 

 called " capitulum " (Kopfchen) is the thickened closing-membrane 

 of the bordered pit, regarding it, on the contrary, as the border itself, 

 that is, the broadened margin of the pit. This and some other points 

 in the anatomy of these structures he illustrates by the action of 

 chemical reagents on the different pits. 



Underground Stomata.^ — E, Hohnfeldt has examined the stomata 

 on the underground axial organs and scale-like leaves of a great 

 variety of species belonging to seventy-one different families. 



On the axial organs the number pf stomata usually increases 

 towards the apex ; but exceptions occur in the lower portion of the 

 aerial stem of Prunella vulgaris, and the green branches of Buhus 

 Idceus, on which there are a greater number than on the upper part ; 

 in the latter plant there are fewer on the aerial than on the under- 

 ground part of the stem. In Lysimachia vulgaris the number is small 

 on both the aerial and underground stem. 



When the ordinary leaves have stomata, this is also the case with 

 the underground scale-leaves, and the number is generally greater 

 towards the apex than at the base ; but they are usually fewer on an 

 equal surface than on the foliage leaves. Trientalis europcea furnishes 

 an exception to this rule, where on a superficies of 1 sq. mm. from the 

 upper, and 1 sq. mm. from the under side of the foliage leaves, there 

 were counted 58 stomata; on the same superficies of the scale- 

 leaves, 150. 



While the foliage-leaves, with the exception of floating-leaves, 

 have almost always more stomata on the under than on the upper 

 side, the reverse is often the case with the underground scale-leaves. 



* Jahrb. wiss. Bot., xii. (1880) pp. 133-60. 



t Bot. Ztg., xxxviii. (1880) pp. 720-29. 



X Hohnfeldt, R., ' Ueber das Vorkommen u. die Vertheilung der Spalt- 

 offnungen auf unterirdischen Pflauzeutheileu,' Kouigsberg, 1880. See Bot. 

 Centi-albi., i. (1880) p. 1161. 



