they stand agape in utter amazement to witness poisonous 'frog-stools' bagged by the score. Ofttimes one gets warned that the plants are 'deadly pisin; but collectors are generally looked upon as harmless lunatics, a climax in this direction generally being reached if a gentleman, in search of Ascoboli and the dung-borne Pezizæ, sits down, and after making a promising collection of horse or cow dung, carefully wraps up these treasures in tissue paper, and puts them in his 'sandwich-box.'"

FIG. 147.-Cyathus vernicosus, or Bird's-nest Fungus.

CHAPTER XIV.

ALGE.

THE Algæ form an important order of cryptogamic plants, comprising, however, the very simplest of all plants. It includes at once some of the smallest and some of the largest of plants, among the former being many of the interesting microscopic organisms referred to briefly in Chapter I. Most of them are marine or freshwater plants, only a few species being found on land. All the seaweeds of our coasts, with their lovely tints and beautiful forms, are Alga. They are characterised by the entire absence of true roots. Many of them are attached to the rocks by pseudoroots; but attachment seems to be the only advantage obtained by this arrangement. Instead of being dependent upon these pseudo-roots for nourishment, they absorb it through every part of their surface. They are entirely cellular in their structure, though a few possess organs closely approaching to vessels. In outward form they exhibit a remarkable amount of variation, many of the higher forms being possessed of thick, solid stems, like tree-trunks, as in Lessonia, which forms submarine forests. In the opposite direction, we have such forms as Protococcus, Desmid, and Volvox, which consist of a single cell.

each, and consequently have neither stem, leaf, nor root.

a

We have elsewhere seen that Protococcus absorbs carbon, and sets free oxygen. In this respect all the Algæ agree, and to this power the denizens of the deep, in all their marvellous variety and infinite number, owe their existence. It is frequently stated that the ocean owes its power of sustaining life to its ceaseless motion keeping it constantly oxygen

d P.--
e b

FIG. 148.

ated. But the animal population of the deep is so enormous, and the consequent consumption of oxygen so vast, that this process alone would be insufficient to keep such an immense body of water pure. The submarine forests, which consist entirely of Algæ, give off an immense volume of oxygen, besides supplying the finny tribes, the crustaceans, and the molluscs, with the staple of their food.

There are several methods by which Alge are reproduced. In the lower forms reproduction takes

place by the repeated subdivision of
an individual plant. In others it is
attained by two individuals throwing
out little processes, which come in
contact, unite, and form a spore.
the higher forms the reproductive
process is correspondingly more com-
plicated. In these two kinds of bodies

In

are formed the Sporangia and Antheridia. Fig. 149 shows a cross section of the stem of a species of

Fucus. C shows the position of the Conceptacles, which contain Sporangia, and P denotes the pores or openings of the Conceptacles. In fig. 150 one of these conceptacles is enlarged.

O is the external orifice (P in fig. 149), P the perispores or sporangia. In some species the Antheridia are contained within the same conceptacle as the perispores; in others they are contained in separate conceptacles on the same or other plants. They consist of ovoid sacs containing two Spermatozoids with cilia. When set free they enter the conceptacle by its external orifice or pore, attach themselves to a perispore, penetrate one of the spores contained therein, and by thus mingling their protoplasms, fertilisation of the spore is effected.

Algologists divide this group of plants into five subdivisions, as follows:

I. Olive-coloured seaweeds (Melanospermea). 2. Rose-coloured seaweeds (Rhodospermea). 3. Green-coloured seaweeds (Chlorospermea). 4. Brittleworts (Diatomacea).

5. Volvoces (Volvocinea).

The first of these (Melanospermea) comprises the various species of Fucus and Laminaria so plentiful on all our coasts. Every visitor to the seaside must be familiar with several species of Fucus, long lines of which are left by the receding tide. Who has not turned over quantities of this leathery jetsam to find the tiny crabs which seek shelter beneath it,

with a motley collection of star-fishes, sea-urchins, mussels, and the remarkable clusters of eggs of the whelk and cuttlefishes? Here, too, it is we find those strange eggs of the dog-fish-Mermaids'

purses as they are popularly called, as though such superior beings as the Mer-folk would be troubled with such things as purses! We do not believe they are possessed of pockets wherein to keep them if they had them.

But you recollect the seaweeds? First of all there is that tough,, brownish species with narrowbranching fronds studded here. and there- chiefly where the frond branches out-with air-bladders, which children are fond of ex

ploding by pressure by pressure between finger and thumb. This is the Bladder Wrack or Fucus vesiculosus, and is most common on all rocky shores, covering as it does great areas of low rocks along the shore. We have painful recollections of this species. Not infrequently have we, in hurrying over the wrack-covered rocks, elated with some choice find, slipped on the fronds of this plant and been hurled flat on our back on the rugged, uneven surface of the rocks. The office of the bladders is, of course, to give buoyancy to the

FIG. 151.-Fucus nodosus,
Knotted Fucus.