634 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
protoplasm of these cells contains a number of smaller and some very 
much larger granules ; the latter are of the nature of caoutchouc, and 
increase in number till they become welded into a solid and extremely 
elastic mass. 
Secondary Xylem of the Apetalse.* * * § — Pursuing his investigation of 
this subject, M. C. Houlbert now describes the structure of the secondary 
xylem in the orders of Apetalse with inferior ovary. 
The structure of the xylem of the Loranthacese is so different from 
that of the Santalaceae that the two families cannot be regarded as 
nearly allied. From the same point of view the Juglandaceae appear 
to form an isolated group of the Apetalae, and not to present any close 
affinity with the Myricaceae. 
The Cupuliferae may be divided, according to the structure of their 
xylem, into the two groups Betuloideae and Castaneoideae. In the former 
the structure of the secondary xylem resembles that in the Betulaceae, 
while in the latter it calls to mind that which occurs in the Urticoideae ; 
the vessels are rounded and nearly always isolated. Judging from this 
character the oaks and chestnuts are probably two groups with a com- 
mon origin. In the genus Fagus there are two different types of 
structure, one ( F . betuloides, &c.) presenting the characters of the 
Betulaceae, the other ( F . sylvatica , &c.) those of the Platanaceae. 
Formation of Rods in Secondary Wood.f — Herr W. Raatz has in- 
vestigated the formation of rod-structures in a number of Coniferae, in 
Hippopha'e rliamnoides, Casuarina equisetifolia, and Salix fragilis , which 
cross the tracheids or vessels at a right angle. They may occur in all parts 
of the wood and secondary cortex, in the root, stem, and branches, in all 
trees that increase by an annual cambium ring. They result from the 
coalescence of tangential walls, which thus causes accumulations of cel- 
lulose. The author argues against the theory of Sanio, that the existence 
of these rods indicates the origin of the cambium from a single initial 
mother-cell. He concludes also from his observations that the cambium 
increases by intercalary division of its cells arranged in radial rows ; and 
that the intensity of growth of the cambium is greater on the xylem- 
than on the phloem-side. 
Fibrovascular Bundles of the Flax.j; — Sig. F. Tognini describes in 
detail the course of the vascular bundles in the root, stem, leaves, and 
cotyledons of Linum usitatissimum. The chief departure from the normal 
structure is that the xylem of the leaf-trace system ends free in the 
epicotyledonary axis, without uniting with the cotyledon-traces. 
Medullary Bundles of the Cichoriacese.g — Herr 0. Kruch states 
that supporting bundles are widely distributed in the pith of the Cicho- 
riaceae. They are always of more or less reduced structure, either con- 
sisting only of sieve-tubes, or containing also phloem-elements, vessels, 
and mechanical cells, the sieve-tubes being always the first formed 
* Comptes Rendus, cxiv. (1892) pp. 1217-8. Cf. this Journal, ante, p. 500. 
t Jahrb. f. Wiss. Bot. (Pringsheim), xxiii. (1892) pp. 567-636. 
X Atti Real. 1st. Bot. Univ. Pavia, ii., 21 pp. and 3 pis. See Bot. Centralbl., 1. 
(1892) p. 337. 
§ Ann. R. 1st. Bot. Roma, iv. pp. 204-91 (15 pis.). See Bot. Centralbl., 1892, 
Beih. p. 114. Of. this Journal. 1890, p. 353. 
