What are they?

[Ruijiang Wang]

Dear all,

When I studied the leaf anatomy of Cyathocalyx (Annonaceae), I found that
many transparent and rectangular or irregular particles are along the
veins. But they are neither crystals nor proteins. What are they?

Three images are pasted on the following website

http://web.hku.hk/~rwang/leaf%20structure.htm

Do hope any feedback and any suggestion will be welcome!

Wishes,

Ruijiang Wang

Dept. of Ecology and Biodiversity
The University of Hong Kong