The Structure of Pachytheca. 
BY 
C. A. BARBER, B.A., 
Scholar of Christ's College , Cambridge. 
With Plate IX. 
0 WARDS the end of 1887 two slides containing sections 
of Pachytheca 1 were placed in my hands by Sir Joseph 
Hooker, and I have prepared the following account of the 
structure of the plant, with the accompanying figures as an 
adjunct to his preceding account. 
Of the two sections only one appears to pass accurately 
through the centre of the organism ; the other appears to 
pass through the middle of the spherical body at a short 
distance from the centre. For clearness’ sake, the description 
will be mainly based upon the first of these two slides. 
There are three zones to be distinguished in the specimen : 
an outer cortical zone composed of parallel radiating fila- 
ments separated by a clear, slightly-coloured mineral matrix ; a 
central part , consisting of a colourless mineral matrix pene- 
trated by filaments in different directions ; and a zone of oval 
bodies separating the cortex from the central part (Figs. 1, 2). 
In the cortex (Figs. 2, 3, 4) the radiating filaments are 
divided into cell-rows by transverse walls. The appearance 
of a filament, generally, is similar to that of a Cladophora . 
The ends of the peripheral cells are not present, since these 
are broken off at various points, and the specimen appears to 
have been abraded. Branching's not at all common. In two or 
1 These are not sections of the specimen, the figures of which (Plate VIII.) 
accompany Sir J. Hooker’s paper. 
[Annals of Botany, Vol. III. No. X. May 1889.] 
