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Discussion Starter · #1 ·
I finally nailed down for certain what I suspected for a while now and especially since we collected honest to goodness H. glomeratus in Florida, which looks and grows EXACTLY like what we've been calling H. micranthemoides all this time. I hope to have some good photos of what I talk about below very soon. I was able to get the opinions of two botanists who are quite familiar with H. micranthemoides to back up my own ID; as established and popular as this plant is, I didn't want to take any chances.

Also, the 'two-leaf' is also definitely not H. micranthemoides. The ID of that one has yet to be pinned down and is proving to be quite difficult. It may not be a Hemianthus at all. Neal, do you know anything about the origin of this one? It would help immensely!

As far as I know, the current names are H. micranthemoides and H. glomeratus as opposed to M. micranthemoides and M. glomeratum. More on that later.

H. glomeratus:
- wet depressions, standing water, drainage ditches
- chasmogamous flowers: they open completely and, in this case, are pollinated by insects. The flowers appear somewhat crown-shaped.
- acute calyx lobes - sepals are joined at the base and the lobes are pointed at their tips
- common in Florida

H. micranthemoides:
- tidal rivers, specifically in places that are exposed at high tide and frequently in sandy/gravelly areas where smaller streams meet the larger rivers
-cleistogamous - the flowers do not open and are self-pollinated
-obtuse calyx lobes - rounded at their tips. The entire flower appears distinctly round.
-extinct?
 

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Mm-hmph. I see so these two plants are very identical, eh.. Interesting.
 

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Spring break is coming up next week, and I will have the opportunity to take some close-up pictures of flowers of the the two leaved variety. Will post them here as soon as I get them. I still have the plant I got from Neil Frank growing emerse.

R33 GTR reported the 2-leaved variety from a river in Puerto Rico:
http://www.aquaticplantcentral.com/forumapc/plant-id/72895-need-id-plants.html
 

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So, all our future recommendations for people to use "HM" in their aquascapes will now be replaced with "HG". :)

That's awesome that you were able to nail this down...but kinda sad at the same time that HM may really be extinct. Happy hunting!
 

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Cavan,
Here is what i can tell you about my 2 leaf variant.

I obtained the plant from an ADA tank, while i was visiting Niigata, Japan in 1995.
When i queried ADA staff in 2000, they said via email:

"We call it "New Pearl Grass"- Hemianthus micranthemoides var. and we call the other species 'Pearl Grass'- Micranthemum micranthemoides . We used to use Hemianthus, but many publication in Japan are using Micranthemum more often. So we use now use Micranthemum."​

Here is a related Dec 2000 discussion on APD and one of my 1999 pictures that shows both variants in my old 125g tank. NPG is on right and what i have been calling HM is on left. (for now, we cannot say for sure what is the plant pictured on the left, since it was growing in that tank over 10 years ago and obtained from an unknown source... and perhaps, i obtained it during a NC collecting trip. I vaguely remember seeing it locally :)). The USDA Data Base says that HM grows in the NE coastal States, from VA to NYS (which is not inconsistent with it appearing in NC) . This range for HM is also documented in Muenscher (1944) and Crow and Hellquist (2000). On the other hand, Godfrey and Wooten, Aquatic and Wetland Plants of Southeastern US (1981) does not mention HM, but does include M. glomeratum and says it is endemic to the penisular FL. Interestingly, HM was the plant of the month in TFH and consistent with what Cavan said, the writeup says "There are some reports that the plant has not been seen in its native habitat since 1941."
 

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Hello Neil,
thank You for the photo! I think, the 2-leaved Hemianthus here in Germany is the same as Your plant from Amano. I've gotten it ca. 10 years ago from Christel Kasselmann as Hemianthus micranthemoides, and Jozef Somogyi showed me the plant in a tank in Bratislava (Slovakia). Seemingly it was cultivated in Europe for decades but mostly the difference from H. "micranthemoides"=>glomeratus was not noticed or thought to be caused by growth conditions.

Here on p. 1 photos of my emersed 2-leaf Hemianthus above and H. glomeratus below:
http://www.aquaticplantcentral.com/forumapc/plant-id/61464-plant-id.html
The flower pics are not so good, but under the microscope the flowers of both plants looked very similar.

Btw., emersed 2-leaf Hemianthus looks very similar to emersed H. callitrichoides "Cuba"!

Heiko
 

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Here is a picture of a flower of the 2-leaved variety, wet mount, taken through a microscope at 40X. The flower looks very much like the flower of H. glomertus. 4 sepals, 2 stamens (anthers broken off), a corolla with three prominent lobes, maybe another lobe that I can't see.

 

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Hello Paul,
the ends of the corolla lobes of Your 2-leaf Hemianthus are lacerated (don't know if the term is correct) just as in my plant. The corolla lobe tips of H. glomeratus are more acute.
[edit]and the upper lip of the corolla is apparently absent, typical of Hemianthus.
 

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The picture of H. micranthemoides in the USDA plants database (labeled Micranthemum micranthemoides) shows a flower with four stamens and rather different shapes to the lobes of the corolla.


As far as I can tell, the flower of our two-leaved variety is similar to the flower for H. glomeratus. Shawn Winterton has a very nice macro picture of the H. glomeratus flower:
 

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Discussion Starter · #14 ·
Cavan,
Here is what i can tell you about my 2 leaf variant.

I obtained the plant from an ADA tank, while i was visiting Niigata, Japan in 1995.
When i queried ADA staff in 2000, they said via email:

"We call it "New Pearl Grass"- Hemianthus micranthemoides var. and we call the other species 'Pearl Grass'- Micranthemum micranthemoides . We used to use Hemianthus, but many publication in Japan are using Micranthemum more often. So we use now use Micranthemum."​
Hmmm... Well, it definitely isn't H. glomeratus or actual H. micranthemoides, but I wonder how that name got attached to it. I suppose we could get in touch with them again to see if they know its original source.

I've actually thought about looking for it in NC. Its last know location was in southern VA (Chickahominy River - this exact location is now inundated by a damn, I'm told) and some commonly associated plants are found in NC, so I suppose it's not out of the question. if you could find a spot outside of the reach of any salt water. Perhaps looking in places slightly outside its known range could pay off. The Mattaponi River in VA is a good spot, I think, even though there are no specimens from there.
http://en.wikipedia.org/wiki/Chickahominy_River
http://en.wikipedia.org/wiki/Mattaponi_River

I believe the TFH article is referencing the Plant Finder.
 

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The stigma for H. glomeratus in the drawing in Pennell's book shows a two-branched stigma. In my wet mount picture, but the stigma seems to be made up of many tiny finger-like structures. Perhaps they are organized into two branches. It is a little hard to tell. There are possibly glandular cells on the filaments of the stamens. they can also be seen in Winterton's picture.
 

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Discussion Starter · #16 ·
OK, time for some pics. All have been taken with a microscope camera. I may still need some practice with it, but I think they turned out well.

First is Hemianthus glomeratus collected in Florida (I believe the corolla is missing):


Next is H. glomeratus sourced from general hobby circulation and grown by Ghazanfar:


Another flower from the same specimen:


Now, here is some REAL, honest to goodness Hemianthus micranthemoides collected in NY (1936 if I remember correctly):


Can anyone tell me what the differences are based on the earlier discussion?

Just for fun, here is the Cuban endemic Hemianthus reflexus. It's just a bit larger on average than H. callitrichoides.


The question of what the current genus is for these species appears to be unresolved. They are sometimes included in Micranthemum. For now, I propose we continue to include them in Hemianthus.
 
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