GERMINATION AND GROWTH 43 
be seen with the naked eye, especially if a thin longitudinal 
section is made. It is also well seen in the water roots of the 
common duckweed (Lemna), and on those developed by a 
cutting of the wandering Jew, when placed in water. Are 
there any hairs on the root cap? Can you account for their 
absence? 
Norte. —For a minute study of the structure of roots, see 67. 
40. Organs of vegetation. — The three parts, root, stem, 
and leaf, are called organs of vegetation in contradistinction to 
the flower and fruit, which constitute 
the organs of reproduction. The for- 
mer serve to maintain the plant’s indi- 
vidual existence, the latter to produce 
seed for the propagation of the species, 
so we find that the seed is both the be- 
ginning and the end of vegetable life. 
41. Definitions.— Organ is a general 
name for any part of a living thing, wi 
whether animal or vegetable, set apart yg. 58.—Seedlings of bean 
to do a certain work, as the heart for in different stages of growth: 
, ec, cotyledons, showing the 
pumping blood, or the stem and leaves plumule and hypocotyl before 
of a plant for conveying and digesting ee i ee anttba 
sap. By “function” is meant the ment. At d the arch of the 
particular work or office that an organ A pe er Pe ene ee 
has to perform. erected itself. 
42. Seedlings of dicotyls. The bean. — Sketch, with- 
out removing it, a bean seedling that has just begun to show 
itself above ground; what part is it that protrudes first? 
Sketch in succession four or five others in different stages of 
advancement. Notice how the hypocotyl is arched where 
it breaks through the soil. Does this occur in the monocotyls 
examined? Do the cotyledons of the bean appear above 
ground? How do they get out? Can you perceive any 
advantage in their being dragged out of the ground back- 
wards in this way rather than pushed up tip foremost? 
