32 
CENTRAL HALL. 
Here, as in all tlie Thallophytes, we distinguish two divisions, 
one of green or chlorophyll — containing plants like Protococcus, 
which lead an independent existence, and another of colourless 
plants like Bacteria^ which, having no chlorophyll, are doomed 
to a parasitic mode of life. 
The rest of the case is devoted to the Algae, Fungi, and 
Lichens. The Algae contain chlorophyll, the green colour of 
which is sometimes obscured by a red or brown colouring 
matter, and include the sea- weeds as well as many fresh- water 
plants. The fungi have no chlorophyll, but live as parasites 
on living organisms, e.g., Bhytisma acerinum, which forms black 
spots on maple leaves, or as saprophytes on dead or decaying 
organic matter, e.g., Penicillium. The Lichens are composite 
organisms, consisting of a fungal and an algal element, which 
live together. 
The second group, or Bryophytes, including Mosses and 
Liverworts, will occupy the central case (not yet arranged). 
Except in the lower forms of these, a main axis, or stem and 
leaves borne upon it, can be distinguished. 
In the third group, or Pteridophytes, including Ferns and 
their allies, which occupy the right-hand wall-case, the plant 
body shows a marked distinction into a stem or ascending axis 
bearing leayes, and a root or descending axis. They are also 
called Vascular Cryptogams, as they contain systems of vessels 
forming bundles of wood and bast, not found in the two other 
groups, which are therefore known as Cellular Cryptogams. 
The last two bays are devoted to the great group of Phanerogams 
or seed-plants, where, besides the distinction of stem, leaf, and 
root, and the development of vascular tissue, we find a structure 
unknown in the Cryptogams, viz., the seed, where the embryo, 
or commencement of a new individual, is developed within and 
protected by one or more envelopes (seed-coats), consisting of 
tissues of the mother plant. 
Bay IX. The left-hand portion of this bay contains specimens of the 
S^Mono^ smaller division of seed-plants, the Gymnosperms, in which the 
cotyledons. pollen falls directly on the naked ovule. In the wall-case the 
upper row of specimens illustrates the form of the leaf, while 
the lower deals with the stem and root. The internal structure 
of these is demonstrated by means of large sections. Important 
