RESTING PERIOD 67 
such as Peas, Clover, Alfalfa, Tomatoes, Melons, Cotton, Fruit 
trees, and many forest trees are Dicotyledons. Each of these 
classes includes a large number of important cultivated plants as 
well as many that are regarded as weeds. . 
Since the classification into Monocotyledons and Dicotyledons 
applies only to the Flowering Plants, such plants as the Larch, 
Pine, Spruce, Fir, Hemlock, which belong to the 
Gymnosperms where there are no true flowers, 
are omitted in this classification. The seeds of 
a number of the Gymnosperms commonly have 
more than two and those of the Pine and Cypress 
commonly have many cotyledons. (Fg. 71.) 
They are polycotyledonous seeds and the plants 
may be described as Polycotyledons. 
The difference in the location of the stored 
food in seeds serves in distinguishing them but 
does not affect their function or commercial 
value. In all types of seeds, the endosperm 
must be absorbed by the cotyledons before it is 
available for the growth of the embryo. This 
absorption occurs before germination in the ex- i 
albuminous seeds but during germination inalbu- Fic. 71.—a, 
minous seeds. Among Monocotyledons albumi- Pine seed _ sec- 
nous seeds prevail, while both types are about tioned lengthwise 
: tc show polycot- 
equally common among Dicotyledons. qledouye. bi Bette 
i F eer : seed germinating, 
Resting Period, Vitality, and Longevity of Seeds |, . san ae 
The function of a seed as the plant’s organ of dons becoming 
dissemination depends upon a number of physi- free from the sced 
: ‘ z 5 coat. Both are 
ological features, of which the chief one is the agen 
ability of the seed to remain alive with the ordi- 
nary life processes so slowed that they seem not to be taking 
place at all. 
Resting Period. — The resting condition is a valuable physio- 
logical feature to the seed, because in this condition the embryo 
can endure cold, heat, dryness, intense light, and various other 
conditions to which the seed is exposed during dissemination. 
How the resting condition is brought about and how it is main- 
tained, often many years, are not thoroughly understood. The 
resting condition is associated with dryness, a condition obtained 
