separated genera as Blasia, Radula, and Preissia, four cells of equal size are formed, arranged round a centre. One only of these cells proceeds to develop into a plant, and the others simply atrophy. In all probability the Hepatica have sprung from some ancestor, in which each spore gave rise to four individuals.

4. Pteridophyta.-According to Farlow,1 instances of apogamy-the loss of sex-such as have just been described as existing among mushrooms, are also exhibited in certain ferns. In some species, the eggs are not fertilized, but the organs of reproduction still persist in a reduced condition; in other species there are no spores, and the prothalli spring directly from the leaves (apospory).

5. Phanerogams.—Some of the PhanerogamsSilene (fig. 58), Melandryum, (fig. 59), Asparagus, etc. exhibit unisexual flowers, but have obviously sprung from species of which the flowers were hermaphrodite.

In Silene maritima (fig. 58) there are hermaphrodite flowers (fig. 58, B), and also unisexual flowers. The female flowers (fig. 58, A) still possess some tiny stamens, each of which is provided with filaments and anthers in a state of degeneration. The male flowers have flowers have non-functional pistils,

1 W. Farlow, Ueber ungeschlechtliche Erzeugung von Keimpflänzchen an Farnprothallien. Bot. Zeit., 1874, p. 180.

2 A. de Bary, Ueber apogame Farne u.s.w. Bot. Zeit., 1878, p. 449.

consisting of an ovary stylus and stigma in reduced conditions.

In Melandryum (fig. 59, A) the female flowers

in the unisexual

flowers, the organs of the opposite sex still exist, though in various stages of degeneration. In many unisexual flowers which have sprung from hermaphrodite flowers Valeriana dioica, for instance no traces of the nonfunctional organs remain.

FIG. 59.-Flowers of Melandryum album. A (to the left), a female flower; to the right, a male flower; e, rudimentary stamens forming a circle at the base of the ovary.

Among the Phanerogams, rudimentary organs

appear not only in the reproductive organs, but in the accessory organs of the flower-the calix and corolla. Many of the Umbelliferae exhibit a reduced calyx.

The corolla persists, though in a very reduced state in cleistogamous flowers (i.e. flowers which never open, and which are self-fertilizing)-such as the Oxalis, Impatiens, Violet, etc. The corollas of

the winter-opening flowers of Stellaria media are much reduced, and for a very obvious reasonthe corolla exists only for the attraction of insects, and there are no insects at that time of the year.

§ 4. Reduced organs in the vegetative apparatus of the Phanerogams.

We have seen that reduced sexual organs are exhibited among the various groups of plants, and we will now mention a few instances of reduced organs in the vegetative apparatus of the Phan

erogams.

1. The embryo within the ripe seed of Phanerogams contains a rudimentary root which develops during germination. In certain Nympheacea—Nelumbium Euryale and Victoria-this root never properly develops.

In other aquatic plants degeneration has gone further; in the embryo of Utricularia, for instance, the root has entirely disappeared.1

1 For further details relating to the roots of the Nympheacea and the Utricularia see Goebel in Pflanzenbiologische Sohilderungen, vol. ii., Marburg, Elwert, 1891-1893.

2. As a general rule, the cotyledons, which are the two first leaves to appear after germination, are formed within the embryo. The ripe seeds of some Anemones, however, contain no traces of cotyledons.1 These are formed, nevertheless, after germination, sometimes sprouting up out of the ground and becoming functional, and occasionally remaining underground, in which case they are quite small, without chlorophyll and nonfunctional (Anemone nemorosa); these underground leaves may fairly be regarded as rudimentary

FIG. 60.-Seedling of

organs.

3. In Lathyrus Nissolia (fig. 60) there are some very small stipules of unimportant function, at the base of the simplified leaves; these reduced stipules are occasionally absent altogether.

4. The foliage organs in the adult Oxalis bulpeurifolia are Lathyrus Nissolia. merely represented by enlarged leaflets. These phyllodes bear reduced leaflets which rapidly disappear. In an adult specimen of the Acacia which has phyllodes, these reduced leaves are absent.

1 E. de Janczewsky, Études morphologiques sur le genre Anemone. (Revue générale de botanique, t. iv., p. 241.)

5. In several plants the assimilative function of the leaves is lost, either because the plant is parasitic or saprophytic, such as Corallorhiza, Rafflesia, Cuscuta and Orobanche, or because the assimilative function is relegated to the stem alone as in the Euphorbia of the desert, Ruscus, Mamillaria,1 Phyllocactus, Phyllanthus, and Mühlenbeckia, or to the roots as in Taeniophyllum.2

In each of these cases the leaves are greatly reduced, and only serve as a means of protection to the functional organs, principally to the flowers and buds, but though very minute they may often be discerned quite easily on the young shoots.

CHAPTER II

SURVIVALS EXIST IN ALL KINDS OF SOCIETIES

IT may be said as certainly of societies as of other organisms that certain modifications have taken place, and that no society actually represents a primitive social organization. All have been submitted to more or less important modifications and have lost some of their early institutions in

1 See fig. 51.

2 See further on the figs. of Phyllocactus (fig. 78), Phyllanthus (fig. 84), Mühlenbeckia (fig. 80), and Toniophyllum (fig. 81).

3 Goebel, Pflanzenbiologische Schilderungen, Bd. i.