BOLTON MICROSCOPICAL SOCIETY. 99 
ture moving slowly over the structure of the sponge, and has noted 
that when the old skeleton remains intact, the living matter that 
issues in the spring from the openings at the top of the statoblasts 
will reclothe their former framework. If it is washed away, the cells 
secrete new spicules, as those of our body secrete new bone.— 
Philadelphia Record. 
BOE TON MICKROSEOPICAL, SOCIETY. 
T the March meeting of the Bolton Microscopical Society an 
interesting paper was given by Mr. Mawson Harvard on the 
“Spore Cases of Ferns,” of which the following is a condensed 
report :— 
Spore cases, which are the provision that nature has made for 
the production, development, preservation, and diffusion of the 
spores, are sometimes called sporangia, theca, or capsules, and 
are collected into groups of varied form, called sovz. 
The forms assumed by these sori are usually distinct spots, 
round or oblong, or lines, more or less extended. The principal 
ones being the punctiform, the oblong or linear, the amorphous, 
and the uwnzversal. 
In most ferns the sori are borne on the under surface of the 
frond, and are then said to be “dorsal.” In others they are pro- 
truded from the edge of the frond, and are called extra mar- 
ginal ; these are often collected round the free extremities of the 
veins, which are surrounded by thin urn-like expansions of the 
cellular tissue. But there are some curious exceptions to these 
usual modes of development. 
The point at which the sorus is fixed to the frond is called the 
receptacle. This receptacle is formed by an expansion of the 
tissue, at some fixed point of the venation, sufficiently constant 
to acquire systematic importance from the fact. 
The spore cases of the greater number of known species of ferns 
are small, roundish, hollow, one-celled bodies, nearly surrounded 
by an elastic belt, which ring is called the aznulus, and these 
ferns are called annulate ferns. Ina few classes the spore cases are 
without any trace of ring or annulus, and are called exannulaze ferns. 
The spore-case itself consists of a thin cellular shell, without 
internal divisions, traversed externally by a single line of short 
transverse parallel thickened cells, which form the belt or ring. 
It seems to be the elasticity of this belt or ring, which, in some 
species of ferns, takes a vertical direction, and in others a horizontal 
one, that causes the case to burst, and liberate the spores. 
In certain annulate groups of ferns the spore cases spring from 
