260 BOTANY AS APPLIED TO VETERINARY SCIENCE. 
2. The stem presents no distinct division into pith, wood, 
and bark, and it increases by the addition of new bundles of 
vascular tissue to its interior; hence the term Endogen. A 
transverse section presents no concentric rings or medullary 
rays. This may be observed in our common reeds ( P/irag - 
mites communis) , and others. 
3. The leaves. —The veins, instead of being spread out in a 
variety of forms resembling a network, run parallel with each 
other, and are connected by simple transverse unbranched 
veins. They are generally simple, linear in shape, and but 
rarely articulated to the stem. Examples may be seen in 
the grasses, meadow saffron ( Colchicum autumnale ), &c. 
4. The flower. —Each part consists of three or some mul¬ 
tiple of that number, as three sepals, six stamens, &c. An 
example is in the white lily ( Lilium candidum ). 
3. ACROGENS OR ACOTYLEDONS. 
This class corresponds with the twenty-fourth, or Cryp- 
togamia, of the Linnean system. They have no true flowers, 
consequently produce no seed; hence the term Acotyledon. 
Their reproductive organs are called spores. Few of them 
have any distinct stem, and in these cases they increase by 
additions to their summits, having the wood in the interior 
arranged in a zigzag manner. This may be observed in 
some of the ferns. Most Acrogens have neither stem, leaves, 
nor flowers. Examples may be seen in the mosses, fungi, 
&c. 
These are the three primary divisions under which all 
plants are classed according to the Natural system; but to 
make the distinctions more clear, I have taken the following 
arrangement from a very useful work to beginners, viz., 
Lindley's ‘ School Botany/ 
Class. 
Wood . 
Leaves. 
Flowers. 
Embryo. 
1. Exogens 
Concentric 
Reticulated 
Dicotyledonous. 
2. Endogens 
Confused 
Parallel-veined 
V 
Monocotyledonous. 
3. Cryptogamia 
or 
Aciogenj 
Sinuous 
or 
0 
Eork-veined 
or 
0 
0 
0 
