64 Exhibits in Natural History. [Sess. 
The first young leaves are always imperfect, but the older 
leaves of many mosses possess a midrib which always proceeds 
from the base. In the row of cells in the middle of the young 
leaf a wall arises parallel to the surface, dividing these cells 
into two. By further divisions and growth of the lower of 
these cells the midrib is formed. The inner cells form the 
conducting tissue, while the outer become thickened and serve 
to strengthen the leaf. The structure of the midrib, like the 
outline of the leaves, varies with the different genera. 
It has already been said that the inner half of the segments 
cut off from the apical cell formed the meristem of the stem. 
This is brought about by repeated longitudinal and transverse 
segmentation. Generally speaking, there is very little differ- 
entiation of tissue, and the absence of a well-developed vascular 
system is accounted for by the ability of mosses to absorb 
nutriment at any point of their surface. 
While special prominence was given to the history of the 
moss plant from the spore to the formation of the antheridia 
and archegonia, attention was also directed to the capsule, but 
a detailed study of it has been left over for another season, 
and may form the subject of a future communication. 
EXHIBITS IN NATURAL HISTORY. 
AT the winter evening meetings during the Session a number 
of interesting objects in Natural History were exhibited by 
members. Amongst these, the Secretary (Mr A. B. Steele) 
showed a specimen of the Jew’s-ear fungus (Hirneola auricula- 
Jude), found in Niddrie grounds. The President (Mr W. C. 
Crawford) submitted a microscopic section of wood from the 
supposed “crannog” at Dumbuck, near Dumbarton. Mr C. 
Campbell exhibited the nest of the long-tailed titmouse. Mr 
A. Murray displayed a very interesting collection of mosses 
gathered by him on Ben Lawers, during the excursion 
described in his paper read to the Society on February 22 
(see pp. 28-40). A large number of microscopic objects 
were also exhibited throughout the Session, including living 
specimens, and slides prepared by members. 
