The Collaborative International Dictionary
Vasculum \Vas"cu*lum\, n.; pl. Vascula. [L., a small vessel.]
(Bot.) Same as Ascidium, n., 1.
A tin box, commonly cylindrical or flattened, used in collecting plants.
Wiktionary
n. A container used by botanists to keep samples viable by maintaining a cool, humid environment.
Wikipedia
A vasculum or a botanical box is a stiff container used by botanists to keep field samples viable for transportation. The main purpose of the valsculum is to transport plants without crushing them and by maintaining a cool, humid environment.
Usage examples of "vasculum".
Jonas stuffed the third creature into the vasculum and snapped it shut.
He threw the vasculum hardit had almost reached midstream when it dropped into the water.
About this time a botanist, complete with vasculum, was noticed working over the heath.
On the other hand, fish obtain their oxygen and expel the carbon dioxide through soft vascula tissues containing many tiny filaments.