flower before this is fully effected, the elastic threads which bind the pollen masses together save The mode in which the

them from being lost. moth's proboscis effects fertilization may be simulated by inserting a bristle into the nectary, leaving it there as long as it would take the moth to feed, and then inserting it into another flower. The pollinia come out of the first flower upright on the bristle, in a few seconds they diverge;

when it is withdrawn from the second flower the stalk is found deprived of its pollen masses.

Some remarkable forms of orchids are given in Figures 46, 47, and 48. The Cycnoches egertonianum is a most singular plant. It will produce for a long time flowers like those marked v, of a pale delicate green, and then suddenly bear an immense raceme of the flowers e, which are unlike them in form, color, and the number growing on one stem.

For some time the same plant, classified by its blossoms, received different names, C. ventricosum, and C. egertonianum.

Several orchids have been classified as different genera which after long study proved to be only the male, female, and hermaphrodite forms of the same plant: the flowers are so different that they were not even referred to the same genus.

The mimetic quality of the orchids has been greatly exaggerated by fanciful writers. Some of them, especially the columns of certain varieties, do look not unlike butterflies, and bees, and birds, but there is not one which could for a moment deceive the most unobservant. It is the oddity of the flowers, their curious suggestiveness of something abnormal, that really makes them such favorites, as well as the extreme rarity of certain varieties.

CHAPTER VIII.

THE MICROSCOPE AMONG THE FLOWERS.

ICOTYLEDONS (named because of the two

D seed leaves which first appear above the

ground) are exogenous plants; that is, the cells which multiply and cause the growth of the plant lie just beneath the epidermis of the stem, or the bark. The members of this group, which live many years, are marked by annual rings of growth. The stem of any sapling or trunk of any tree sawed across shows this. Each year the growth of the preceding year loses its protoplasm; the cell walls turn into wood. Each year's growth forms a new ring; the loose open tissue being the summer's growth, the dense close tissue the winter's, and these two layers are the ring. Nothing is better known than that a tree which is girdled dies, and yet few people feel that all of the central woody part of a tree is really dead, and only the cambium layer just below the bark is living. This living layer adds to the wood by its yearly circles on one side, while it adds to the

bark by pushing in between the old cells new ones, and so enlarging its girth as the tree grows. Every dicotyledon, even the simple annual plants, show a wonderful differentiation of tissues in stems and roots. The conducting vessels, lactiferous vessels, glands, and so forth, are without number.

The main interest of this great class of plants, however, lies in the flowers and their modes of fertilization. The flower with its pistils and stamens, its petals and sepals about their floral axis, are usually arranged in concentric whorls, or in a closecoiled spiral, thus producing the rosette effect so characteristic of blossoms.

In many flowers the suppression of certain organs obscures the concentric arrangement of the petals. In some varieties one, and in some another, of the separate whorls may be absent, or reduced to a single representation, and in extreme cases the flower may be reduced to a single organ, staminate or pistillate. When the corolla consists of a single whorl of petals, they often cohere and form a bell-shaped flower. The pistils and stamens which occupy the centre of the rosette are merely leaves modified so as to fulfil their functions. Like the sporangia of the ferns, which are borne upon the under surfaces of