a8 BRITISH FERNS. 
eveh these are again and again divided, but the 
divisions have not received any name of general 
Lastly, we come to the fructification or seed: this 
is contained in little round cells or cases, commonly 
called “capsules,” and these are often surrounded 
by a jointed ring which terminates in a short stalk; 
when ripe the capsule splits open, and its clastic 
ring, by a series of jerks, throws out the seeds, 
‘These capsules are also called “theca” and “ spo- 
trangia,” and are generally seated on the back of 
the frond in little clusters or masses, which are also 
called “sori,” but I have carefully avoided these 
| words, thinking the English terms “capsules” and 
“clusters” or “masses” better in all respects ; more 
correct, more expressive, and more intelligible. These 
_ Clusters or masses of capsules are often covered with 
@ thin filmy scale called the «jnvolucre” or “in- 
”; and this has for a long time been used 
for the purpose of artificially dividing Ferns into 
groups; but for this purpose its form is too varied, 
‘its. presence too uncertain, Be any ase 
mhatqver 9, mode in which the masses 
dusium 
