The British Association at Dundee. 
369 
Morphological and Palasobotanical Papers. 
Professor Bower contributed an interesting paper on “The 
Origin of Indusium in some Ferns.” Starting from the “ Pterid- 
type ” with the marginal flap of the fertile leaf covering the sori, 
the more primitive types of Blechnum show only a slight thickening 
of the flap about the point of greater curvature. But in the more 
advanced types such as Blechnum brasilieuse a very considerable 
foliar expansion occupies the same position. Here the “ indusial” 
flap is morphologically the leaf margin and the expansion is a new 
formation. The next step is seen in Woodwardia and Doodya, 
where the elongated sorus of Blechnum is divided into rows of 
separate sori, but this “ indusium ” is still a marginal flap. 
This origin of the indusium is distinct from that in other types 
of ferns, and it is possible now to distinguish at least five different 
phyletic origins of protective structures passing under the general 
name of indusium. 
Professor Bottomley read a paper on “ The Root-Nodules of 
the Podocarpeae.” They are present in all genera of this group and 
are arranged in two distinct rows along the sides of the roots. 
They are developed from the pericycle cells opposite the tw'O proto- 
xylems and are evidently modified lateral roots which are arrested 
from normal development by the entrance of bacteria into the 
cortical cells, in the first instance through the root-hairs. The 
bacterial tissue of the nodule, which surrounds its central stele, 
remains active for one season only, after which most of the cells 
lose their contents and their walls become thickened by bars 
of cellulose. The following spring a new mass of bacterial tissue 
is formed from the pericycle, and the old cells are squeezed out to 
form an outer protective zone. The formation of new bacterial 
tissue each year is characteristic of all root nodules concerned with 
nitrogen fixation. 
Professor D. Ellis communicated an account of the structure 
and multiplication of Cladothrix dichotoma. 
Mr. R. B. Thomson contributed some evidence with regard to 
the relative age of the Abietineae and the Araucarineae. Two forms 
have been considered to indicate the great age of the Abietineae, 
Pityoxylon chasense from the Permian and P. conwentzianum from 
the Carboniferous. Dr. Gothan has shown that the reputed age of 
the latter cannot be considered as authentic, and the former is now 
shown to possess no structural features which are Abietineous. 
There is now no known Abietinean form, either in or earlier than 
the Trias, where the first undisputed Araucarian, Woodworthia, 
makes its appearance. Evidence from that and later species does 
not fulfil the demands of the Abietinean theory of the ancestry of 
the Araurcarineae. 
The structure of a new specimen of Sutclijffia was described 
by Dr. Ethel de Fraine. The chief points in its structure were 
the presence of a great thickness of secondary wood round the 
steles and meristeles, which are further surrounded by anastomosing 
strands of wood and bast. The latter recall those in certain genera 
of Cycads, and the view was upheld that the origin of the Cycad- 
