“Is there?” said Daisy.  “I do not see anything else.”

“Pardon me—­you do see it.”

“Then I do not know what it is,” said Daisy laughing.  Absolutely, the sober, sober little face had forgotten its care, and the eyes were alight with intelligence and curiosity, and the lips were unbent in good honest laughter.  The doctor raised himself up to a sitting posture.

“What do you call those grey and brown patches of colour that hide your rock all over?”

“Grey and brown?” said Daisy wistfully—­“those are just the colours of the rock, aren’t they?”

“No.  Look close.”

“Why, Dr. Sandford, what is it?  It is not the rock—­some of it is not—­but here is a spot of yellow that is nothing else, I think.”

“You must learn not to trust your eyes, Daisy.  That is something that grows; it is not rock; it is a vegetable.  If I had my pocket lens here I would shew you; but I am afraid—­yes, I have left it at home.”

“Why it is!” cried Daisy.  “I can see now—­it is not rock.  What is it, Dr. Sandford?”

“Lichen.”

“What is that, sir?”

“It is one of the lowest forms of vegetable life.  It is the first dress the rocks wear, Daisy.”

“But what does it live on?”

“Air and water, I suppose.”

“I never knew that was a vegetable,” said Daisy musingly.  “I thought it was the colour of the rock.”

“That goes to prepare soil for the mosses, Daisy.”

“O how, Dr. Sandford?”

“In time the surface of the rock is crumbled a little by its action; then its own decay furnishes a very little addition to that.  In favourable situations a stray oak leaf or two falls and lies there, and also decays, and by and by there is a little coating of soil or a little lodgment of it in a crevice or cavity, enough for the flying spores of some moss to take root and find home.”

“And then the moss decays and makes soil for the ferns?”

“I suppose so.”

Daisy stood looking with a countenance of delighted intelligence at the great boulder, which was now to her a representative and witness of natural processes she had had no knowledge of before.  The mosses, the brakes, the lichen, had all gained new beauty and interest in her eyes.  The doctor watched her and then scrambled up to his feet and came to her side.

“Look here, Daisy,” said he, stooping down at the foot of the rock and shewing her where tufts of a delicate little green plant clustered, bearing little umbrella-like heads on tiny shafts of handles.

“What is that Dr. Sandford?”

“Something wonderful.”

“Is it?  It is pretty.  What is it, sir?”

[Illustration]

“It is a plant somewhere between the mosses and the lichens in its character—­it is one of the liverworts, and they are some of the first plants to go in advance of superior vegetation.  This is called Marchantia.”