Andreas Wistuba (A.Wistuba@DKFZ-Heidelberg.DE)
Wed, 21 Sep 1994 09:14:56 GMT+1

Dear Matthew, Jan, Joachim and all other readers interested in

yesterday Matthew asked about thoughts reagerding pitcher shape of
some species which have small lids so that no rain protection is
evident. The same question I was thinking about a lot already and
have some thoughts.
As I grow all the species you mentioned and also saw them in the wild
I want to make some suggestions how I think these pitchers work:

1.) N. inermis and dubia:
Whereas the upper part of the pitcher is infundibulate, the lower
is tubulate. As you mentioned the pitcher fluid is what I would call
slimy. If you simulate rain in the greenhouse you can see that the
pitchers due to the increased weight bend down a few degrees, so that

the rainwater can easily run away. I think because the fluid is so
and the lower part quite narrow, one could treat the fluid in the
half as some kind of column. The rain has little chance of disrupting
mixing this column which is supported by both, the narrow shape and
the consistence. Insects (very small ones at least in the greenhouse,

which are cought very efficiently) sink down and can not be washed
out. As the rain runs off quickly there is not much danger of the
pitcher fluid being diluted and nutrients being washed away.

Nepenthes inermis

0 = unprotected liquid
x = slimy liquid-column

\ 00000/

2.) N. lowii:
The pitchers consist of two parts. The lower one is bowl shaped while

the upper one is plate like and I would think that it contributes to
insect-attraction if you think of the red coloration. The channel
between both parts is quite narrow, so that a mixing of the fluids
which are in the lower part, where also the digestion takes place
to be very unlikely when a normal rain goes down. I think the bowl
shaped lower part is an alternative construction to the column of N.
inermis and dubia but results are the same.
In both cases a mixing and washout of the nutrient-rich soup of the
lower part is prevented and the upper part can freely be disigned by
evolution for a maximum of trapping efficiency. The construction for
me seems to be quite similar to Heliamphora, by the way. However as
the pitchers are too static another way of water run-off was chosen.
Another (but quite similar) design was chosen in case of N.
Here the "bowl" is bent upwards again along the tendril (sorry for
limited ability to express myself in English language) so that a
is created which is quite isolated.

N. lowii

x = protected liquid
o = unprotected liquid
\ 000000000000000/
\ 00000000 /
II ___\ 00000 /__
II _/ 0x0x0x0x0x0 \_
II _/ xxxxxxxxxxxxxxxxx\
II /xxxxxxxxxxxxxxxxxxxxx\
II IxxxxxxxxxxxxxxxxxxxxxI
\\ \xxxxxxxxxxxxxxxxxxxx/

N. ephippiata

x = protected liquid
o = unprotected liquid

I \ _________
I x \ \ ooooooo /
I xx \___I ooooo /
\ xxx0x0x0x000 /

3.)N. ampullaria:
At most places where I saw them they were growing under trees in
deep shade. In this environment there is not much danger of a hard
rain since most of the water is trapped by the trees and a lot of
uns down at the stems of trees.

Lid hairs:
I have no real idea however do you have any idea of the nature of the

huge slime deposits which are produced by N. lowii and N. ephippiata
between the hairs? I tasted this slime and it was not sweet (maybe a
very dull sweetish taste?!) but I must admit that I never checked
the slime really consists of. If however the slime consists of
(sugars or proteins) useful for insects like ants the hair might
as a ladder to ease the way to the food.
Another possible function which seems to be more likely to me could
be to support the slime which might work as an attractant for insects

and to fix the deposits so that they are not washed away by rains. If

one considers that the slime deposits reach sizes of more than one
cubic-centimeter a need for a support seems to be very likely to me.

I know that all my ideas are pure speculations but I hope this is OK
that forum.

All the best


Andreas Wistuba
Phone: +49-621-705471 Fax: +49-621-711307