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Loraine Kohorn <[log in to unmask]>
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- JBS-L - Josselyn Botanical Society discussion list of the University of Maine <[log in to unmask]>
Wed, 11 Jun 2003 14:55:12 -0400
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 From the work of Bierzychudek and others, it has been shown that
jack-in-the-pulpit  (and other species of Arisaema) are sex-switchers;  sex
is determined in any season according to resource availability,  generally
with larger plants becoming female.    If fruit production (by "females")
depletes resources over a number of years, plants can switch back to being
males,  then change in another year to being female  as carbon stores
accumulate. .   In our jack-in-the-pulpit species, there is no particular
threshhold size where they change sex - i.e. there may be much overlap in
size between  males and females,  but larger plants still are most likely
going to be female.
So it is not so much about leaf number,  as about photosynthetic area, and
that those plants with a single leaf, if they are flowering at all, are
likely only to have adequate resources to express themselves as males.

On the ticks:  I don't know about long-term trends in Maine, but wetter
years have typically given rise to more ticks, in my experience.

At 10:02 AM 5/27/2003 -0400, you wrote:
A member of my wildflower class brought to my attention a discrepancy in
the literature I gave out about the sex life of the Jack-in-the-Pulpit.
In a write up from Marilyn Mollicone to JBS, 1992, she states that the
male Jacks have two leaves and the females one leaf as a rule.
In another article (Paulette Bierzychudek, Natural History Magazine,
1982) it is stated that the males have one leaf and the females two.
So, being the curious botanist, I went into my own garden (yes, ideal
growing conditions for all my Jacks for years) and found that they all
have two leaves and that there are 3 males, 9 females, and several
single leaves with no inflorescence.
Please shed some professional light on this quandary and reply to all of
Many thanks,