"How do they manage to perch on a tree with feet of that kind?" "With the exception of the wood-duck, this family never perch; they pass the day in dabbling in the water, and sleep upon its surface, or among the reeds." "Then they must always be wet." [Illustration: "They were at once saluted by a platoon fire."] "Not so; nature has covered the feathers of web-footed birds with an oily substance, which renders their plumage quite water-proof. Ducks are gregarious, and migrate from one locality to another, according to the seasons. They are so common on the lagoons which surround the city of Mexico, that sportsmen scarcely will be troubled shooting them." While l'Encuerado was preparing dinner, I and my companions walked along the edge of the stream. Before long I discovered some water-cress--a lucky discovery for travellers who are confined constantly to animal food. Lucien examined the small white flowers, which have obtained for all its family the name of _Cruciferae_; these vegetables contain an acrid and volatile oil, which gives them strong anti-scorbutic qualities. The cabbage (_Brassica oleracea_), turnip (_B. napus_), radish (_Raphanus sativus_), and mustard (_Sinapis alba_), are of the crucifera order. To this list we must also add the horse-radish, the colza, the seed of which produces an oil well adapted for lighting purposes; the _crysimum_, or hedge-mustard, a popular remedy in France for coughs; the shepherd's purse, which the Mexicans use as a decoction for washing wounds; and the _Lepidium piscidium_, employed by the natives of Oceanica for intoxicating fish, so as to catch them more easily. "You quite forget the _cochlearia_, or scurvy-grass, so useful to sailors as a remedy for scurvy?" said Sumichrast. "You are right; but I think I've said enough about the _Cruciferae_ for Master Sunbeam to remember." A few paces farther on, while we were looking for insects under the leaves of a shrub, Lucien drew back in surprise at seeing it covered with the pretty little creatures called tree-frogs (_Hyla viridis_). Instead of flying towards the water, these reptiles made for the woods. Sumichrast explained to the young naturalist that tree-frogs have sticky disks on their feet, and by the aid of this mechanism they could move about on leaves and even on smooth surfaces. "In Europe," he added, "the peasants shut them up in bottles half full of water, and assert that the animal predicts good or bad weather by either coming up to the top or keeping under the water. The tree-frog, like all its fellows, buries itself in the mud during winter, and remains torpid. This lethargy, which in glacial climates has the effect of preserving it from hunger, must in Mexico have some other cause, for in the latter country it can find food all the year round. The skin of the tree-frog secretes a poisonous matter." "Come here and look at an apple-tree!" cried Lucien, suddenly.