are produced singly on the upper side ne near the bake re 
the Jeaf. .The macrosporangia contain a small number of 
macrospores, the microsporangia a large number of micro eo 
spores. 
naked, z.e. not enclosed in an ovary ; and z. ANGIOSPERMIA, 
in which they are so enclosed. The alternation of genera- 
tions 1s in them conceaied in the formation of the seed. The 
pollen-grain corresponds to the microspore, and the embryo- 
~ sac to the macrospore of the Heterosporous Vascular Crypto- 
gams. Gymmnosperms comprise the Cycadee, which have a 
simple stem and pinnate leaves; and the Condfere, with 
branched stem and simple usually acicular leaves. Angio- 
sperms are again divided into two classes, Monocotyledones 
and Duecotyledones. In the former the embryo has only a 
single cotyledon, the vascular bundles of the stem are dis- 
persed, and the prevalent number in the parts of the flower 
is 3. In Dicotyledons the embryo has almost always two- 
opposite cotyledons, the vascular bundles are united in the 
stem into a more or less complete ring, surrounding a central. 
(axial) pith, and the prevalent number in the parts of the 
flower is 5 [or 4]. 
It is necessary again to state very distinctly that there are a number 
of plants which must be assigned, in consequence of their natural affi- 
nity, to a class in which they could not be included if its distinguishing 
characteristics were rigidly interpreted. If, however, in sucha case the 
principle of the classification were to be rigidly enforced, we should 
fall into the greater evil—because still more opposed to the idea of a | 
natural system—of separating arbitrarily what are naturally related. 
Even the best natural system must, therefore, be either not altogether 
systematic, or must be unnatural, because any systematic attempts to con- 
strain free Nature in the fetters of an arrangement which is foreign to — 
her, must leave out of account tl:e numerous transitional forms which 
occupy intermediate places between the principal types. 
Phanerogamia or Flowering Plants are classified into’ 
tivo Aaatiank :—1. GYMNOSPERMIA, in which the ovules are 
