www.photomacrography.net :: View topic - Hook of avens burr (Geum macrophyllum)
www.photomacrography.net Forum Index
An online community dedicated to the practices of photomacrography, close-up and macro photography, and photomicrography.
Photomacrography Front Page Amateurmicrography Front Page
Old Forums/Galleries
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Hook of avens burr (Geum macrophyllum)

 
Post new topic   Reply to topic    www.photomacrography.net Forum Index -> Technical and Studio Photography -- Macro and Close-up
View previous topic :: View next topic  
Author Message
rjlittlefield
Site Admin


Joined: 01 Aug 2006
Posts: 17426
Location: Richland, Washington State, USA

PostPosted: Thu Jun 25, 2015 9:47 pm    Post subject: Hook of avens burr (Geum macrophyllum) Reply with quote



Geum is a genus of plants commonly called "avens". They are in the same family as roses and apples, but instead of producing a single fruit like those plants do, avens form a large burr-like assembly of seeds that each come equipped with a single hook suitable for grabbing hair on a passing animal.

Shown above is how the hook forms. As described in "Flora of the Pacific Northwest" (Hitchcock, 1973, pg 212), "styles strongly geniculate and jointed, persistent portion the longer, hooked at tip".

In other words, the female part of the flower, which receives pollen, is formed into a long basal section that ends in a hook, followed by a shorter section that contains the stigma, which is shed as the seed matures. On the left side of the image is a slightly less mature seed, with its stigma section still attached; on the right side the stigma section has been shed and all that's left is the basal hook.

Bear in mind, "basal" is a relative term. That hook is still quite some distance away from the actual seed:



Moving farther out, here is an entire burr, with its front removed by pulling seeds away from the central core.



Moving in again, here is a crop of the above, sized to include a little more than the length of one entire seed, including its hook. On the left side of the image I believe you can see some of the stamens, thoroughly dried up and devoid of pollen at this point.



Length of each single seed is about 8 mm, including its hook.

These are Geum macrophyllum, the "Large-Leaved Avens". They're from that trip I took to the mountains last week, having sat in a vase of water since then. I guess they're not completely dried out, judging from the number of live aphids that still haven't left them.

Identifying this plant was a bit amusing. I didn't bring home much material, and I struggled to identify what I had from just the burrs in hand and vague memories of brief glances at the rest of the plant. Finally I found the right place in one book, then in another book the detailed structure of the burr nailed it down. A few minutes later -- and a complete coincidence as far as I know -- my wife came in from our backyard garden, carrying burrs that looked remarkably similar to what I had in hand. Fortunately she keeps really good records. It too was a Geum, 'Lady Stratheden' for whatever that means, planted in 2006. For all the delicacy of its name, however, the garden Geum has a much more robust flower. Here's the comparison, 'Lady Stratheden' on the left and its wild cousin Geum macrophyllum on the right (complete with aphids Smile ).



Shot with Canon T1i using Mitutoyo 5X and 2X objectives with Raynox DC-150 tube lens, and with Olympus 80mm bellows macro lens. Jansjö LED illumination, mostly with latex glove fingertips for diffusion. Backgrounds are various paint chips from the local hardware store.

--Rik
Back to top
View user's profile Send private message Visit poster's website
Carmen



Joined: 10 Feb 2015
Posts: 273
Location: Buenos Aires

PostPosted: Sat Jun 27, 2015 2:36 pm    Post subject: Reply with quote

beautiful and informative! thank you for sharing Rik Very Happy
Back to top
View user's profile Send private message Visit poster's website
rjlittlefield
Site Admin


Joined: 01 Aug 2006
Posts: 17426
Location: Richland, Washington State, USA

PostPosted: Sun Jun 28, 2015 10:30 am    Post subject: Reply with quote

Thanks, Carmen -- I'm glad you found it interesting.

--Rik
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    www.photomacrography.net Forum Index -> Technical and Studio Photography -- Macro and Close-up All times are GMT - 7 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group