March 09, 2018

Is that a Jack? No, There be Dragons and Quinatums in the Pulpits!

After the recent addition of "5-leaved Jack-in-the-Pulpit" Arisaema quinatum to iNat, I decided to go looking for them using Weakley's Flora 2015 (p144), to dig them out by keying all A.triphyllum and A.dracontium ID's on iNat that are located in states where Weakley has them in-range (wide swath from TX to NC). It was easy in the beginning:
3-lobe Jacks with a thick 4-10mm diam. spadix held upright and a long spathe hood flopped over it are A.triphyllum,
5-lobe Jacks with a thin 1-3mm diam. spadix that leans over, and a short pure-green spathe hood held flat are A.quinatum, and
7+-lobe Jacks with a 20cm long spadix shooting out above the hood are A.dracontium : Green Dragons.

It was easy, until I got to the observations with no spathe or spadix (gone to seed), or immature.
Then I got a few more ID'd by noticing that the Jacks have 2 leaves on the stalk (each 3-lobed for A.tri-phyllum, and a 5-lobe primary and 3-5-lobed auxilliary leaf for A.quinatum), while the Dragon has only a single leaf ever.

Here is the good-and-hard part:

I then had a bunch of 5-lobed Arisaema things with no spathe/spadix, and no clear shot of the stems. What to do? Could easily be A.quinatum or A.dracontium, and I didn't really want to be that guy who took your RG A.triphyllum away and said "... genus Arisaema, not enough detail to determine to species ...". Here I'll thank @wdvanhem and @etantrah for being a bit reluctant on some of my initial IDs of a few of these edge cases (all in TN, at the edge of the range). Gentlemen you caused me to have to really dig in and figure it out, and so here it is:

5-lobed A.quinatums and 5-lobed A.dracontiums can be very difficult to tell apart given only a leaf-from-above image, I have made this error myself, thinking 5-lobed A.dracontium to be rare. Not so, in fact, all Dragons go through a D5 stage. Some have even commented that Dragons and Jacks often grow together, and while that might happen occasionally, I would dispute that this is common, but rather state that, based on the many edge cases I've been looking at, young 3-lobed Dragons in with older plants have been casually called A.tryphyllum Jacks. I'll submit this for your consideration: (here Dragon-N or DN means an A.dracontium with an N-lobed leaf) a Dragon-19 with 1:3(new)-1:5(old) ratio lobes a Dragon-15 with 1:5 ratio a Dragon-7 with 1:2-1:3 ratio
Which leads to the idea that perhaps dragon leaf lobes do two interesting things as they grow:
- lobes get longer with age, going from elliptical (1:2 ratio) to oblong (1:3 ratio) to almost linear (1:5 ratio).
- new lobes are added at the two termini of the petiole, sprouting out of the previous junior-most lobe, throughout the season. They are not born fully shaped like buckeye, Carya or Juglans leaves.

Then we get these even more elucidatory observations, of colonies of A.dracontium growing at various maturities (they have no seed dispersal means (beyond birds), they just flop over, so plants come in groups if conditions are good).
Here we can clearly see the round D3 leaves lengthening and adding lobes to become elliptical D5 leaves, and then oblong D7+ leaves ... I Love Science! showing 1:1 ratio D3, 1:2 ratio D5, and 1:3 ratio D10 leaves showing 1:1.5 ratio D3, 1:2.5 ratio D5, and 1:3 ratio D7 leaves showing 1:1.5-1:2 ratio D5s, D6(emerging lobe), and 1:3 ratio D7 leaves too many D3, D5, D7's to sort!
all of course without a second leaf on the stalk (so not A.triphyllum)
So, there you have it, those D3's are not Jacks, but Baby Dragons!

So now I'm going back in again to fix all those last edge cases. I rest my case, Thanks for reading this far!
So far, about 45 Arisaema quinatum and 6+ A.dracontium have been found (in around 700+ other Arisaema reviewed).

Posted on March 09, 2018 05:09 PM by lincolndurey lincolndurey | 5 comments | Leave a comment


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