The wall between them is perforated, giving passage to coarse strands of protoplasm.
The melting pans are generally circular vessels, fitted with a perforated false bottom, on which the sugar to be melted is dumped.
With another form of gas stove coke is used in place of the perforated asbestos; the fire is started with the gas, which, when the coke is well alight, may be dispensed with, and the fire kept up with coke in the usual way.
Cells of this type are often called trumpet-hyphae (though they have no connection with the hyphae of Fungi), and in some genera of Laminariaceae those at the periphery of the medulla simulate the sieve-tubes of the higher plants in a striking degree, even (like these latter) developing the peculiar substance callose on or in the perforated cross-walls or sieve-plates.
It is evident that accurate knowledge of the character and structure of the rock-formations in petroliferous territories is of the greatest importance in enabling the expert to select favourable sites for drilling operations; hence on well-conducted petroleumproperties it is now customary to note the character and thickness of the strata perforated by the drill, so that a complete section may be prepared from the recorded data.