THE PARTS OF THE SEEDLING. 
LT 
the cotyledons, and the leaves of this pair differ in shape 
from those which arise from the succeeding portions of the 
stem. 
- 21. Classification of Plants by the Number of 
their Cotyledons. — In the pine family the germi- 
nating seed often displays more than two coty- 
ledons, as shown in Fig. 6; in the majority of 
common flowering plants the seed contains two 
cotyledons, while in the lites, the rushes, the 
sedges, the grasses, and some other plants there 
is but, one cotyledon. Upon these facts is based 
the division of most flowering plants into two 
great groups: the dicotyledonous plants, which have 
two seed-leaves, and the monocotyledonous plants, 
which have one seed-leaf. Other important differ- 
ences constantly accompany the difference in 
_ number of cotyledons, as will be seen later. 
Fia. 6. — Ger- 
minating 
Pine. 
c, cotyledons. 
