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may 12 1893 
JOURNAL 
OF THE 
ROYAL MICROSCOPICAL SOCIETY. 
APRIL 1893. 
TRANSACTIONS OF THE SOCIETY. 
III. — The President's Address : On the Anatomy of Mosses. 
By Robert Braithwaite, M.D., &c. 
{Read 18 th January , 1893.) 
Last year, as you will remember, I called your attention to the 
process of impregnation in the higher cryptogams — the Archegoniata 
— and traced their development so far as the formation of the young 
plants ; I propose now, at least in the Bryophyta, to bring before 
you their further progress to the perfect state, and summarize what 
the Microscope has revealed to us of their structure. 
We saw that the spores on germinating produced a branched 
confervoid protonema, from one of the lower joints of which the 
growth of an individual plant commences. This takes place by a 
short tubular prolongation from the side of the protonemal cell, 
which divides by several transverse septa, and its apical cell becomes 
the commencing bud. Oblique septa arise and subdivide, the first 
segmented cells being the foundation of the axis, from the lower end 
of which fine hair-like rhizoids are thrown out, by which the little 
plant fixes itself to the substratum— the earth, rocks, stones, or bark 
of trees— and absorbs nutriment ; these radicles may be at once dis- 
tinguished from protonema by the cells being more elongated and 
the septa between them oblique to the axis. In Catharinea undulata 
(one of the Polytrichaceae) the roots are very long and coiled round 
each other like a cable ; and, again, in many species the roots bear 
nodules or tubercles which are capable of developing protonema and 
young plants. The upper end of the axis elongates into a stem of 
variable length, which throws off lateral cells to form leaves, and in 
nearly all mosses becomes coated to a greater or less extent with a felt 
of rhizoids, adventitious radicles or radicular tomentum, rufous, fuscous, 
or blackish, by which the stems are matted together into dense tufts, 
and are thus enabled to retain water like a sponge. 
In a transverse section of a strong stem we may observe a central 
pith of elongated thin- walled cells, and an outer cylinder of wood- 
cells, and between these the parenchym cells contain chlorophyll and 
starch, while some of them have their walls greatly thickened, so that 
1893. l 
