The stems are frequently characterized by aeration channels, which connect the aerial parts with the parts which are buried in practically airless mud or silt.
In this plant the aeration is conducted by blowing in air at the base of the condenser.
For the successful preparation of potable water from sea-water, the following conditions are essential: - Ist, aeration of the distilled product so that it may be immediately available for drinking purposes; 2nd, economy of coal to obtain the maximum of water with the minimum expenditure of fuel; and 3rd, simplicity of working parts, to secure the apparatus from breaking down, and enable unskilled attendants to work it with safety.
The efficiency of drainage, digging, hoeing and like operations is accounted for by the manner in which they promote aeration of the soil, raise its temperature and remove its stagnant water.
But research showed that this process of nitrification is dependent on temperature, aeration and moisture, as is life, and that while nitre-beds can infect one another, the process is stopped by sterilization.
Related to the physiological drought, such plants possess some xerophytic characters; and, related to the physical wetness, the plants possess the aeration channels.
Again, the well-known action of earthworms may be said to be a biological work; but the resulting aeration of the soil causes edaphic differences; and earthworms are absent from certain soils, such as peat.
Even when all the conditions above mentioned in regard to texture, water-holding capacity, aeration and temperature are suitably fulfilled the soil may still be barren: plant foodmaterial is needed.
They serve probably for the aeration of the gonads by admitting to their vicinit y water with its dissolved oxygen; they never serve as genital ducts, since the generative products are always dehisced into the stomach and pass out by the mouth.
The aeration of the water is effected by blowing air into the steam before it is condensed; as an auxiliary, the storage tanks have a false bottom perforated by fine holes so that if air be injected below it, the water is efficiently aerated by the air which traverses it in fine streams. After condensation the water is filtered through charcoal.