function of circulating and distributing nutriment through the colony.
In this respect the Asiatic species differs very widely from its African relative, whose nutriment is largely composed of boughs and roots.
In the case of the common drone-fly, Eristalis tenax, the individual, from a sedentary maggot living in filth, without any relations of sex, and with only unimportant organs for the ingestion of its foul nutriment, changes to a creature of extreme alertness, with magnificent powers of flight, living on the products of the flowers it frequents, and endowed with highly complex sexual structures.
The point common to all Pteridophyta is that from the first the gametophyte is an independent organism, while the sporophyte, though in the first stages of its development it obtains nutriment from the prothallus, becomes physiologically independent when its root develops.
The commentaries of the Arabians in this respect supplied nutriment more readily assimilated by the pupils than the pure text would have been.