FERN TRIBE 105 
The second kind of organ is the archegonium, corresponding to the ovary of a 
flowering plant. Within its centre is a free germ-cell, and when some of the 
antherozoids have found their way to it and combined with it, this becomes 
fertile and produces fronds. Then the prothallus wastes away and ceases to 
exist. Diagrams of these organs will be found on Plate E. 
The frond of the fern arises from the rhizoma or rootstock, which may be 
generally described as a creeping underground or horizontal stem, though 
in some exotic species it rises erect, and emerging from the earth, resembles 
the shaggy trunk of a palm. Some of our own species assume the vertical 
attitude, though their crowns rise only a few inches above the ground. The 
rhizoma of our native ferns is usually covered with shaggy scales or hairs, 
which sometimes, as in the Common Brake, are so fine and numerous, that 
they form a surface of velvety down. Sometimes this rhizoma sends out so 
many shoots, that they form a firm network beneath the surface of the soil ; 
but more often this portion of the fern occupies little space in the ground. 
The true roots of ferns are the fibres which descend from the rootstock. 
The native species of Fern described are between forty and fifty in 
number: but some authors make them more, and others less, numerous. The 
Horse-tails and Club-mosses are fern-like plants, and not true ferns, though 
they are commonly called jointed or leafless ferns. None of our ferns in 
their ordinary state attain more than six or seven feet in height, and we 
rarely find any, except the Common Brake or the Royal Fern, nearly so high. 
When growing in large numbers, they are sometimes conspicuous on the land- 
scape ; but nowhere in Britain do they give, as in tropical climates, a charac- 
teristic feature to the scenery, or assume the dimensions of trees. Herbaceous 
ferns belong chiefly to temperate and colder countries ; but in the warmer 
regions, shrubby ferns cover the ground, forming, like our Common Brake, 
an undergrowth in woods; while the herbaceous species are found chiefly 
growing upon trees, where, clinging sometimes to the topmost boughs, or 
investing the rugged trunks with their green sprays, they display a luxuriance 
and beauty unknown to the British fern. ‘'Tree-ferns, too, of exquisite grace 
and beauty, grow in the tropical forest. Whether, however, of humble 
growth, or rising to the height of twenty or thirty feet ; whether herbaceous 
or arborescent in habit, they have all so much similarity of general appear- 
ance, that they are readily known to be ferns, even by those who have never 
studied the botanic description of plants. On the forks of some of the 
old timber trees in Australia grow also the Stag’s-horn Fern (Platyceriwm 
alcicorne), as large as the largest cabbage, the frond resembling the palmated 
antlers of the moose and reindeer. This luxurious growth extends to a 
variety of other herbaceous and shrubby species, which hang upon the stems 
and branches of trees, or rise as an undergrowth to the towering ferns from 
whose tops spring large fronds, often eight or ten feet long, thrice-pinnated, 
and so graceful and light that the smallest breeze sets them in tremulous 
motion. The works of Baron Humboldt abound in descriptions of the ferns 
in the forests of South America ; and every writer on New Zealand tells of 
the ferns of that island. Humboldt remarks that the arborescent ferns 
produce the densest of shade in the American forests, by reason of their 
number and luxuriant growth. He describes some of the old trunks of 
| Iv.—14 
