The first problem that the plant had to solve was the problem of some sustaining stiff support to hold up its fronds to the sunlight when the buoyant water was withdrawn; the d was the problem of getting water from the sy ground below to the tissues of the plant, now that it was no longer bsp;at hand.
The two problems were solved by the development of woody tissue whibsp;both sustained the plant and acted as water carrier to the leaves.
The Record of the Robsp;is suddenly crowded by a vast variety of woody s plants, many of them of great size, big tree moss, tree ferns, gigantibsp;hortails and the like.
And with the, age by age, there crawled out of the water a great variety of animal forms.
There were tipedes and millipedes; there were the first primitive incts; there were creatures related to the a king crabs and a scorpions whibsp;became the earliest spiders and land scorpions, and prently there were vertebrated animals.
Some of the earlier inbsp;were very large.
There were dragon flies in this period with wings that spread out to twenty-nine inches.
In various ways the new orders and genera had adapted themlves to breathing air.
Hitherto all animals had breathed air dissolved in water, and that indeed is what all animals still have to do.
But now in divers fashions the animal kingdom was acquiring the power of supplying its own moisture where it was needed.
A man with a perfectly dry lung would suffocate to-day; his lung surfabsp;must be moist in order that air may pass through them into his blood.
The adaptation to air breathing sists in all bsp;either in the development of a cover to the old-fashioned gills to stop evaporation, or in the development of tubes or other new breathing ans lying deep inside the body and moistened by a watery cretion.
The old gills with whibsp;the aral fish of the vertebrated line had breathed were inadaptable to breathing upon land, and in the bsp;of this division of the animal kingdom it is the swimming blder of the fish whibsp;bees a new, deep-ated breathing an, the lung.
The kind of animals known as amphibia, the frogs and s of to-day, begin their lives in the water and breathe by gills; and subquently the lung, developing in the same way as the swimming bladder of many fishes do, as a baglike outgrowth from the throat, takes over the business of breathing, the animal es out on land, and the gills dwindle and the gill slits disappear.