ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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Hypeeoum procumbens — which have true laticiferous vessels, the red latex, 
similar to that of Glaucium and the Fumariaceee, which they contain 
when young, is replaced subsequently by a yellow liquid ; and he traces 
a transition between the laticiferous system of Papaveraceaj and that of 
Fumariaceaa. 
Herr W. Zopf,* * * § on the other hand, regards the alleged laticiferous 
vessels of the Fumariacese as alkaloid-receptacles. 
Formation of Secondary Medullary Ray s .f— According to Herr E. 
Schmidt, the initial of a secondary medullary ray always differs more or 
less in form from the cells formed later. This initial cell is not the 
result of a sudden change in fuuction of a cambium-cell, but of the 
intercalation of tracheids among the delicate younger cells lying towards 
the cortex, the newly formed medullary-ray-cell following the example 
of such a tracheid. After the cambium-cell has cut off a number of 
tracheids, the first medullary-ray-cell appears as the result of a horizontal 
division in the upper part of a cambium-cell ; and the cell thus cut off 
assumes more and more a triangular or quadangular form. In the forma- 
tion of a medullary ray from a cambium-cell, its upper or lower end is 
cut off by a horizontal septum ; and the end thus cut off is the initial of 
a medullary ray. 
Cells of the Mesothece of Hydrangea. Sig. M. Geremicca de- 
scribes the peculiar form of the cells of the mesothece, the hypodermal 
layer in the anther, in Hydrangea hortensis. They are thickened by 
long narrow bands which run in a parallel direction on the lateral walls 
of the cells, and unite below, so as to form a kind of open cup. Instead 
of “fibrous cells” or “band-cells,” as these cells have previously been 
called, the author proposes to term them the thickening cells of the 
mesothece. 
Stem of Asclepiadeae.§ — Herr K. Treiber has undertaken a detailed 
examination of the anatomical structure of the stem of a large number of 
species of Asclepiadese. Isolated procambial buudles were never found, 
but always a closed procambial ring, out of which are differentiated not 
only the primary bast-fibre groups and the primary internal and external 
phloem-groups and vessels, but also the parenchymatous tissue and the 
cambium. Besides the external and internal phloem (in relation to the 
xylem), some species have bundles of phloem in the pith ; while occasion- 
ally there is a paraxylary phloem in the thin-walled xylem-parenchyme. 
The primary vessels are chiefly collected into four groups, corresponding 
to the insertions of the decussate leaves ; a few lie scattered irregularly 
between these. The special characteristics of the climbing species are 
also described. 
Anatomy of Nicotiana.||— Dr. J. B. de Toni and Sig. J. Paoletti 
describe in detail the anatomical structure of the various organs of 
Nicotiana Tabacum. Among the more important points is the observa- 
* Ber. Deutsch. Bot. Gesell., ix. (1891) pp. 107-17. 
f ‘ Beitr. z. Kenntu. d. seeundaren Markstraklen,’ Berlin, 1890, 32 pp. and 2 nls 
See Bot. Centralbl., 1891, Beih., p. 514. 
J Bull. Soc. Bot Ital., i. (1892) pp. 37-9. 
§ Bot. Centralbl., xlviii. (1891) pp. 209-18, 241-9, 273-81, 305-13 (2 pis.). 
|| Ber. Deutsch. Bot. Gesell., ix. (1891) Gen.-Versannnl.-Heft, pp. 42-51 (2 pis.). 
