654 
THE PRINCIPLES OF BOTANY. 
of a lower kind of vegetable organism. In this way it is that 
it has been concluded that the Cryptogamic vegetation even 
exceeds that of flowering plants in its number of species ; but if 
we consider that these lower tribes differ according to sur¬ 
rounding media, we may, perhaps, conclude that absolute 
species, so difficult to determine, are not so many as has been 
thought, but that very diverse forms are either stages in 
development or have been produced differently from the same 
spores, having been acted upon by a different medium. 
If, however, we only cursorily glance at the positions in 
which the plants of our lowest class are found, we shall have 
reason to see that they must be infinitely varied, as both salt 
and fresh waters are full of them, varying from the minute 
Algae, thousands of individuals of which might rest on the 
point of a pin, to the Sea tangles, some of which are many 
yards in length. 
Then, again, every decaying heap of vegetable matter, 
each decomposing stick, and even the roots of dead grasses, 
become nidi for different forms of fungi; whilst the stems 
and branches of trees, and the surface of each rock or stone 
afford resting places to a long list of Lichens. 
With so many families of plants in the same class it 
becomes necessary that we should adopt a method of grouping 
them to which we can readily refer; w^e therefore, in this 
])lace, direct attention to the grouping advanced by Professor 
Lindley first, which proceeds upon the principle of forming 
the larger divisions into which he terms Alliances. 
Alliances of Thallogens. 
1. Algales. —Cellular flowerless plants, nourished through 
their whole surface by the medium in which they vegetate, 
living in water or very damp places, propagated by zoospores, 
coloured spores, or tetraspores. 
2. Fun gales. —Cellular flowerless plants, nourished through 
their thallus (spawn or mycelium), living in air, propagated 
by spores, colourless or brown, and sometimes inclosed in 
asci; destitute of green gonidia. 
3. Lichenales. —Cellular flowerless plants, nourished 
though their whole surface hy the medium in which they 
vegetate, living in air, propagated by spores, usually inclosed 
in asci, and always having green gonidia in their thallus. 
These characters sufficiently indicate family Alliances, 
which latter are again subdivided into natural orders, but we 
shall not follow out these in detail, but shall seize upon 
opportunity to present drawings and descriptions of some of 
