Why do some trees, as the Oak, the Beech, and the Hornbeam, retain their leaves to a late period of autumn?

Because the life of the twigs on which they grow is not sufficiently vigorous to throw them off, after the brown colour indicates that they are dead.

Why have some plants been termed the Poor Man’s Weather-glass?

Because they shut up their flowers against the approach of rain.  Linnaeus, however, thinks, that flowers lose their fine sensibility, after the anthers have performed their office, or when deprived of them artificially.  Sir James Smith also observes, that some species are sometimes exhausted by continued wet; “and it is evident that very sudden thunder showers often take such flowers by surprise, the previous state of the atmosphere not having been such as to give them due warning.”

Many flowers have a regular time of opening and shutting.  We have already mentioned the Marigold; the goat’s-beard is vulgarly called “John go-to-bed at noon,” from its closing at mid-day; and at the Cape of Good Hope there is a “four o’clock flower,” because it invariably closes at that time.  The common daisy is, however, a readier example, its name being a compound of day’s and eye—­Day’s-eye, in which way, indeed, it is written by Ben Johnson.  It regularly shuts after sun-set, to expand again with the morning light.  Thus,—­

  The little dazie, that at evening closes.

Spenser.

  By a daisy, whose leaves spread,
  Shut when Titian goes to bed.—­G.  Withers.

Leyden sings of moist or rainy weather foretold by daisies.  Thus we may examine a whole field, and not find a daisy open, except such as have their flowering nearly over, and have in consequence lost their sensibility.

The daisy is one of the pet flowers of the poets.  Chaucer is ecstatic in its praise, and calls it his “owne hartes’ rest;” Burns, “Wee, modest, crimson-tipped flower;” and Wordsworth, in beautiful and touching simplicity, has addressed several poems to “the poet’s darling.”

Appended to Richard’s valuable “Elements,” is the Horologium Florae, (timepiece of Flora,) or a table of the hours at which certain plants expand and shut, at Upsal, 60 deg. north latitude.  The earliest Meadow Salsafy opens from 3 to 4 A.M.; and closes from 9 to 10 A.M.  The latest A.M. is the Mesembryanthemum Modiflorum, (used in the manufacture of Maroquin leather,) which opens 10 to 11 A.M., and closes at 12 P.M.  The latest opening P.M. is the Cactus Grandiflorus, 9 to 10 P.M., and closing at 12 P.M., thus remaining open only two or three hours.  Other flowers, we may add, are so peculiarly delicate, as scarcely to bear the contact of the atmosphere.