SOME FACTS ABOUT ARUMS. 
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SOME FACTS ABOUT ARUMS. 
We are all familiar with the fact that plants absorb and 
decompose carbonic acid, and that while keeping the carbon 
to build up their tissues, they restore nearly the whole of the 
oxygen to the air for the benefit of the animal world. 
All this is true, but it is not the whole truth. Some 
plants—the whole race of fungi for instance—breathe as 
animals do, and exhale carbonic acid ; and the tiny yeast 
plant, as it multiplies in the wort, produces carbonic acid in 
such quantities that the gas may be seen flowing over the 
sides of the beer-vat. Nor is even this all. All plants take up 
oxygen and give off carbonic acid, and that at all hours of 
the day and night, but especially at night; though the 
quantity given off is so small compared with that which is 
absorbed that it is apt to escape notice. Whether performed 
on a large or small scale, however, this giving off of carbonic 
acid is true breathing; it means that carbon has been 
oxidised or burnt, and therefore that more or less heat must 
have been produced. Yet plants, like frogs, are, with certain 
exceptions, always cooler than the surrounding air, owing to 
the constant evaporation or perspiration going on through 
the myriads of minute pores with which their leaves are 
studded. There are 120,000 pores in a square inch of lilac 
leaf; some leaves have 800 to the square inch, others 
170,000 ; and through these water is constantly being per¬ 
spired as invisible vapour. A single sunflower plant has been 
known to perspire as much as twenty-two ounces of water in 
the course of twenty-four hours ; and thus, although some 
small amount of carbon is always being oxidised, the leaves 
are kept cool. Plants are especially active in giving off 
carbonic acid at certain times—namely, when they first begin 
to sprout from seed and when they blossom ; and when a 
number of seeds are all sprouting together, as in the prepara¬ 
tion of malt, the heat is quite sufficient to be noticeable. 
If the bud of some large flower, such as a thistle or 
cucumber, be isolated under a bell-glass, when just on the 
point of expanding, it will be found that its temperature 
rises from a half to a whole degree centigrade (l|-° F.) In 
many blossoms the heat is much greater than this, and is 
like that from a stove or a feverish hand. It is especially 
noticeable in plants of the arum tribe. We all know the 
common white arum, or “ arum lily” as some people call it, 
with its large glossy leaves and snow-white sheath or 
“ spathe” surrounding the golden sceptre-like column, which 
botanists call the “ spadix.” 
