ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
547 
especially in reference to the deposition of silica. In addition to the 
silicification of the walls of the epidermal cells, there occur in the epiderm 
special “ silica-cells,” the contents of which consist of a white mass of 
amorphous silica. Similar structures are found also in other grasses. 
The arrangement of the vascular bundles is the normal arrangement of 
Monocotyledons. 
Changes produced by Mycorhiza in the Cells of the Host-Plant.* * * § — 
MM. P. A. Dangeard and L. Armand have studied the effects produced 
on the tissues of the root of OpJirys aranifera by its endotrophic myco- 
rhiza. The filaments of the fungus penetrate the outer layers of cells, 
forming a ball in the cortical layers. They produce hypertrophy not 
only in the nucleus of the cells invaded, but in those also of adjoining 
cells. The cytoplasm of the cells attacked is gradually for the greater 
part consumed, 'while the nucleus remains active and intact. In the 
meantime the hyphae of the invading fungus become more or less disor- 
ganised, the small nuclei disappear, and a gummy exudation of an 
unknown character takes place. The nucleus of the host-cell, when 
attacked by the parasite, breaks up by fragmentation, the fragments 
pressing towards the surface of the ball by rhizopod-like prolongations. 
In the cells attacked there are two kinds of nucleus, some with ordinary 
reticulate structure and numerous vacuoles, others whose substance is 
finely punctated and without vacuoles. The nuclei of the invaded cells 
maintain their activity after the parasite has become completely disor- 
ganised. 
“ Sereh-”Disease of the Sugar-Cane, f — From a very exhaustive 
examination of a great number of varieties of the sugar-cane grown under 
many different conditions, Herr A.Wieler contests Janse’s theory that 
this wide-spread disease is due to stoppages in the conducting tissue 
caused by a parasitic schizomycete, Bacillus Sacchari, The gummy 
stoppages are of the same nature as those frequently found in other 
plants under healthy conditions, the gum being exuded into the vessels 
and intorcellular spaces from living cells. Schizomycetes are frequently 
present, but they are saprophytic, not parasitic, the result rather than 
the cause of disease. 
(4) Strupture of Org-ans, 
Inflorescence of Compositae.J — Herr A. Weisse finds the number 
of ray-flowers in the capitule of Composite to be subject to similar 
laws to those of the phyllotaxis of leaves. It is to a certain extent 
dependent on nutrition. 
Cohesion and Chorisis of Foliar Leaves.§ — According to observa- 
tions made by Herr G. W. Maly (chiefly on Weigelia rosea , which varies 
greatly in the number of parts of the flower), the normal number and 
arrangement of the vascular bundles is not departed from when either 
cohesion or chorisis takes place of members of the same whorl. A pri- 
mary vascular bundle enters into each member of the calycine, corolline, 
and staminal whorls ; those belonging to the sepals and stamens being 
* Le Botaniste (Dangeard), v. (1897) pp. 289-313 (8 figs.). J 
t Beitr. z. wiss. Bot. (Fiinfstuck), ii. (1897) pp. 29-140 (1 pi. and 23 figs.). 
X Jahrb. f. wiss. Bot. (Pfeffer u. Strasburger), xxx. (1897) pp. 453-83 (1 pi.). 
§ SB. K. Akad. Wiss. Wien, cv. (1896) pp. 269-80 (2 pis.). 
