262 Principles of Plant Culture. 
plantlets appear, after which note the number of each lot of 
seeds of which the cotyledons appear above the surface. 
Development of plantlets (45-47). Devote several exercises 
to a thorough study of the development of plantlets of the 
bean, pea, wheat, Indian corn, pumpkin etc. Seeds of the 
different sorts should be planted, to furnish the plantlets, on 
several successive days, beginning at least 10 days in ad- 
vance. 
Not all seeds may be deeply planted (48). Plant seeds of 
the bean, pea, Indian corn and wheat in 6-inch flower pots, 
at 3 different depths, viz., 4 inch, 3 inches and 6 inches from 
the bottom; place the pots in a warm place for 3 weeks, 
after which carefully remove the soil, noting the germina- 
tion of the seeds in the different layers. 
Vigor of plantlet proportionate to size of seed (49). Plant 
large and small specimens of navy beans, by themselves, in 
greenhouse saucers, and permit them to germinate. The 
smaller seeds usually germinate earlier than the larger, but 
they produce more slender plantlets which soon fall behind 
the others in development. 
Plantlet visible in the seed (54). Boil samples of various 
kinds of seeds until they are fully swollen, after which re- 
quire the students to dissect them and to seek out the plant- 
lets. Lenses, needles and forceps are very useful in this 
work. 
The cotyledons a storehouse for food (60). Remove the 
cotyledons of some bean plantlets growing in a flower pot or 
saucer, leaving those of other plantlets intact. After a week, 
note the result in the checked growth of the mutilated plants. 
Vascular bundles (68). Study these as shown in the stalk 
of Indian corn, in the leaf stems of various plants and in 
the leaf scars on the stems of plants. 
Cambium layer (69). Locate this in sections of various 
dicotyledonous stems, including the potato tuber; also note 
the absence of the cambium layer in monocotyledonous 
stems. 
Root-hairs (101). Study these as illustrated when seeds 
germinate in the seed tester. Germinated radish-seeds, left 
in the seed tester two or three days, usually develop root- 
hairs in great abundance. Also search out the root-hairs 
in potted plants. Emphasize the difference between root- 
hairs and root branches. 
bets Te, 
