Marigold seed will work their way through clothing. What is this called?

I stumbled and fell in to a pile of marigolds that I was gathering for the trash**. Seed worked their way through two cotton shirts and a long sleeved silk undershirt. I had to pick them out individually. They had hooks or barbs too small to be seen with a magnifying glass. I cannot find an image online that shows the hooks or barbs or whatever.

Do we have no magnified pictures of seed online?

What is it called when seed move using hooks or barbs?



**(Water cost here are too high for composting. I may even discontinue marigolds in borders.)

 

There's a photo of Marigold seeds on the USDA Plants website here.

You get the same effect from several other seeds; Wild Barley is particularly well known for it (pic).

The barbs help drive the seed into soil to sow itself, and also to attach to animal fur (or clothes!) for transport to new areas.

 

Resin, I'm fairly sure that the OP was referring to Tagetes, not Calendula... and I imagine you are too. ;-)
Here are the seeds from "marigold"(Tagetes):
http://www.google.ca/search?client=...4Bw&biw=1459&bih=995&sei=o7udUNPrI4jNiwLL84Aw

 

Yes, I was referring to Tagetes. I was looking for magnified pictures of seed. It appears USDA may, in some places at least, call them ''close up'' pictures. If there is not a vast source of images for ''close up'' or magnified then there should be. I should think.

I will begin my image search again with ~ Tagetes "close up" and see what happens. Thanks.

Addendum edit Nov 14: by doing an image for ~ Tagetes seed "close up" ~ I found a fairly good picture. It looks like the seed have a scale like surface that is reminiscent of fish scales, hence they would work their way through a fabric but would be difficult to pull out except in one direction.