Cuar. XVIIL] CONCLUSION. 367 
there is the well-known fourth class of parasites (such as the 
mistletoe), which are nourished by the juices of living plants. 
Most, however, of the plants belonging to these four classes 
obtain part of their carbon like ordinary species, from the 
atmosphere. Such are the diversified means, as far as at 
present known, by which higher plants gain their subsis- 
tence. 
forming a tower-like structure round 
each of these openings. There are 
no glands on the surface of the 
pitchers, and the fluid with which 
they are often partially filled is 
simply collected rain-water. Adven- 
titious roots are numerous and com- 
monly enter the cavities of the 
pitchers. Delpino (quoted by Treub) 
believes that the pitchers serve to 
collect ants, &c., whose dead bodies 
may supply food tothe roots. Treub 
on the other hand believes that the 
drowning of ants within the pitchers 
is accidental rather than wilful on 
the part of the plant. He points out 
that no arrangement for retaining 
the ants exists, and that the adven- 
titious roots supply ladders by which 
they may escape; moreover the ants 
are as often as not found alive and 
well within the pitchers. Treub is 
inclined to consider that the pitchers’ 
function is as stores or cisterns of 
water; but their use in the economy 
of the plant cannot be considered as 
definitely settled.—F. D.] 
