ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
489 
the tuber be partially plunged in water, a considerable development of 
the lenticels takes place, and they become hypertrophied. 
Development of the Root.* — M. P. Lesage makes some observations 
on the root of a Phaseolus which he grew in a humid atmosphere. In a 
root of the second order which was much longer than the primary root, 
the following striking differences were noticed. 
The portion outside the water was covered with numerous root-hairs ; 
near the water these hairs elongated, while in the w r ater they were much 
shorter, and finally disappeared altogether. In a transverse section it 
was seen that the cortical layers in the air contained smaller elements 
than those in the water, and in the central cylinder the xylem was 
proportionately more lignified in the aerial portion. The root of the 
bean was made the subject of similar observations. It was found 
that when the numerous secondary roots were suppressed, the primary 
root was covered with numerous absorbing hairs. 
Differentiation of the Phloem in the Root.f — While studying the 
anatomy of the roots of Allium Cejpa , M. P. Lesage was struck with the 
early differentiation of the phloem. This was also found to be the case 
in the roots of Anthurium Andreanum and Odontoglossum citrosinum, and 
the progress of the differentiation of the phloem was especially well 
marked in Athyrium Filix-femina. The author concludes by giving a 
list of plants in the roots of which the cells of the phloem are differ- 
entiated before those of the xylem. 
Medullary Phloem in the Root4 — M. J. Herail calls attention to 
the fact that certain plants belonging to the Gamopetalae possess phloem 
on the inside of their conducting bundles, and that these bundles are 
known as bicollateral bundles. The author proposes to give to this 
inner phloem the name of medullary phloem. M. van Tieghem, in one 
of his papers, describes this formation in the adventitious roots of 
Cucurbita maxima. It is also present in the roots of Vinca major and 
V. media , but seems to be absent in V. minor. 
Anatomical Researches on Carex.§ — M. Bordet has paid special 
attention to the anatomical structure of the genus Carex , and the follow- 
ing is a resume of the author’s conclusions: — (1) The genus can be 
divided into four groups by means of the structure of the rhizome ; the 
two first being characterized by the presence of xylem-vessels which are 
either collateral or concentric ; the two others by a cortex formed of cells 
with small intercellular spaces, or by aeriferous canals formed by the 
separation of cells. (2) The stem furnishes no characters applicable 
for purposes of classification. (3) Considerable variation is to be found 
in the leaves of the different species of Carex. 
Structure of Apocynaceae.||— Herr M. Leonhard has examined the 
anatomical structure of a considerable number of species belonging 
to this order, and gives the following as the more important results: — 
In the species specially examined in this respect ( Vinca major 
* Comptes Rendus, cxii. (1891) pp. 109-10. 
f T. c., pp. 444-6. % T. c., pp. 823-5. 
§ Rev. Gen. de Bot. (Bonnier), iii (1891) pp. 57-69 (3 figs). 
|| Bot. Centralbl., xlv. (1891) pp. 1-6, 33 40, 65-70, 97-101, 129-34 (2 pis.). 
1891. 2 M 
