156 THE ROCK SPLEENWORTS. 
and spreads its fronds in green rosettes with very decor- 
ative effect. The stipe and rachis are a shining dark brown 
and the tiny, roundish, or slightly elongated pinne, with 
entire or toothed margins, are scattered along the latter 
on very short stalks. Sometimes they are slightly dilated 
on the upper side at base. The whole frond is seldom 
more than eight inches long and half an inch wide. The 
number to each plant depends upon its strength and 
vigour. Fromten to twenty is nearthe normal number, 
though plants with more than fifty living fronds have been 
collected. The sporangia are borne in linear sori on the 
backs of ordinary fronds, several on each pinnule and ob- 
lique to the mid-vein. This species has also been known 
to produce a few sori on the upper surface of the pinnules. 
Although so small and delicate, the fronds last through 
the winter and spring. Then, instead of the entire frond 
dying, only the pinnules fall, leaving the polished dark 
rachids standing in a circle about the new growth. One 
seldom findsa plant without these relics of other days 
which often greatly outnumber the living fronds. It is 
said that only the early sterile fronds last through the 
winter, but this needs verification. 
A few years ago, it was discovered that under certain 
conditions the fronds are capable of movement. The 
phenomenon is placed on recordin the Botanical Gazette. 
The observer found that by quickly bringing a pot con- 
taining the growing plant from the ordinarily shaded 
position into sunlight, or even bright daylight, the fronds 
made rapid motions back and forth ina direction at 
right angles to the plane of the frond and “ more rapid 
than the second hand of a watch, but with occasional 
stops in the course of each half vibration.” Only the 
fruiting fronds have been found to move thus and these 
