378 PINGUICULA VULG ARIS. Onar. XVL 
complete re-expansion in 16 hrs. 30m. Nitrogenous 
fiuids act for a shorter time than nitrogenous sub- 
stances; thus, when drops of an infusion of raw meat 
were placed on the midrib of a leaf, the incurved 
margins began to unfold in only 10 hrs. 37 m., and 
this was the quickest act of re-expansion observed by 
me; but it may have been partly due to the distance 
of the margins from the midrib where the drops lay. 
We are naturally led to inquire what is the use of 
this movement which lasts for so short a time? If 
very small objects, such as fibres of meat, or moderately 
small objects, such as little flies or cabbage-seeds, are 
placed close to the margin, they are either completely 
or partially embraced by it. The glands of the over- 
lapping margin are thus brought into contact with 
such objects and pour forth their secretion, afterwards 
absorbing the digested matter. Butas the incurvation 
lasts for so short a time, any such benefit can be of 
only slight importance, yet perhaps greater than at 
first appears. The plant lives in humid districts, and 
the insects which adhere to all parts of the leaf are 
washed by every heavy shower of rain into the narrow 
channel formed by the naturally incurved edges. For 
instance, my friend in North Wales placed several 
insects on some leaves, and two days afterwards (there 
having been heavy rain in the interval) found some of 
them quite washed away, and many others safely 
tucked under the now closely inflected margins, the 
glands of which all round the insects were no doubt 
secreting. We can thus, also, understand how it is 
that so many insects, and fragments of insects, are 
generally found lying within the incurved margins 
of the leaves. 
The incurvation of the margin, due to the presence 
of an exciting object, must be serviceable in another 
