CLASSIFICATION OF PLANTS. 221 
plant; but very minute and constant attention should be directed 
to the ovule and the seed, so that a pocket magnifier of moderate 
power is absolutely necessary in examining plants on this system.” 
We can only give an outline of this great scheme, following it up 
with a short notice of the orders, and filling up the sketch with a 
few details of the species most interesting toman. The object of 
a systematic arrangement of plants being to bring together groups 
according to their apparent relationship to each other, that adopted 
by Dr. Lindley classes them as—(1) Thallogens, from @éXapoc, the 
bridal chamber ; (2) Acrogens, from axpos, topmost, and yevaw, to 
produce ; (3) Rhizogens, from pfopa, a root; (4) Endogens, from 
evéov and yervaw, produced within ; (5) Dictyogens, netted, from 
ourve, a net, and yevecda, to be; (6) Gymnogens, from yuproe. 
naked ; (7) Exogens, from e& and yeveo8ar, to grow by external 
additions. 
The Acrogens are here identical in their limits with the Acoty- 
ledons of De J ussieu, the Exembryonate of Richard, the Celullares 
of De Candolle, the Agame of various authors, and the Cryptogamia 
of Linneus. The term itself is, however, only applicable literally 
to flowerless plants, which possess a stem growing like the Exogens, 
80 that the stemless plants are classed as Thallogens. This is, 
however, but an artificial character; and some recent botanists 
allogens as a section of Acrogens. 
ASEXUAL OR FLOWERLESS PLANTS: 
A Thallus is a fusion of root, stem, and 
leaves into one general mass, and Thallo- 
i. THALLOGENs . ba Stems and leaves impercep- j gens are also destitute bn flowers, without 
ble ig , and they multiply by the 
| formation of spheroids, called spores, in 
) \ their interior or upon their surface. 
) ( Beyond Thallogens are multitudes of 
qT, AcRoGENs "aren Stems and leaves quite per- } stems distinctly separated; some o om. 
ceptible, having the spiral filament whichis supposed 
to belong to a higher structural development; 
finally they multiply by reproductive spores 
like the Thallogens. Their stem, however, 
does not i iameter, but at 
not increase in di b their 
) summit, as the name of the class indicates. 
