170 
and not the spores of the mature plant which correspond to 
pollen-grains. Hven in the Selaginella, which has sexual 
differentiation in its microspores and macrospores, the micro- 
spores give origin still to true antherozoids requiring the 
intervention of water. Apart, then, from the’ valid mark 
involved in the distinction between Flowering and Flowerless 
plants, Phanerogams and Cryptogams may also be accurately 
described as air-fertilised and water-fertilised; in doing which 
we indicate a gap which no theory can bridge over. But, 
when we have thus got our first great division of Cryptogams, 
we do not know what to do with it. It is, in fact, an un- . 
manageable ageregate of groups separated from each other by 
such tremendous intervals as, for instance, that between the 
Diatom and the Tree-fern. The botanist is obliged to treat it 
as the zoologist has treated the cognate term Invertebrate, 
that is, to break it up mto more natural series. It is a mere 
question of names whether these should be called sub-kingdoms 
or not. As to their mdependent value and wide divergence 
there is no difference of opimion. Provisionally we may , 
establish three of these sub-kingdoms, the Thallophytes, 
Muscinee, and Pteridophytes, or, speaking roughly, the Algal 
type, the Moss ‘type, and the Fern type. First comes the 
Thallophytes, including the Alge, Fungi, and Lichens, the 
Characew being considered as Algw in deference to the pre- 
ponderance of authority. 
Perhaps no other division of plants includes such vast 
diversity in form, size, and mode of re-production. It links 
the minims of the vegetable world, the Diatoms, Micro-fungi, 
and Oscillatoriacee, with the huge kelp of the Pacific Ocean, 
one of the longest stems in the present epoch. But they all 
agree in consisting of cellular tissue to'the exclusion of fibro- 
vascular bundles, in the absence, more or less complete, of a 
differentiation into root, stem, and leaf, and in the great 
complexity, with few exceptions, of their reproductive pro- 
CeSSeS. 
Those not acquainted with natural science and more familiar 
with mathematical methods may consider this a very vague 
definition. But this difficulty is inherent in the subject. 
Nature, or rather living nature, abbors hard-and-fast: lines. 
She refuses to run into our moulds, and shuts her eyes to our 
neat systems of classification. With reference to plants in 
general, there is scarcely a single statement which can be 
affirmed of them all without exception. We can say little 
more of them collectively than that they live and grow. For 
the fungi prevent us from predicating of all plants that they 
feed upon inorganic materials, that they contain starch, that 
