86 BOTANY 
seems to press less hardly than that of any other 
element. 
The following satisfactory method may also be 
employed. Split ordinary corks into strips about half 
an inch in thickness, and from these make little rafts 
by uniting them in pairs with the splints of wooden 
matches. Float one raft on each solution and place 
across the splints of each a small piece of butter muslin 
in such a way that its ends hang into the liquid. Now 
place on each piece of muslin a few mustard seeds. 
These, being supplied with moisture by the water lifted 
by the muslin, soon germinate, and, by the varying 
vigour of their growth, indicate the relative importance 
of the different elements the solutions contain. It must 
be remembered that any seedling is able after germina- 
tion to grow for a time by drawing on the reserves of 
food contained in the seed. 
SUMMARY. 
The Root fixes the plant in the soil and procures its 
nourishment therefrom. Most dicotyledons have a tap 
root, and most monocotyledons adventitious roots. The 
root is positively, the stem negatively geotropic. 
Gravity attracts the one and repels the other. The 
root is positively hydrotropic. The root is negatively 
and the stem positively heliotropic. The Root-cap 
protects the meristem of the growing point. Elongation 
takes place just behind the growing point. Root-hairs 
are cells of the epidermis which, by osmosis, receive 
water and dissolved minerals from the soil. They are 
produced just behind the growing point and are short 
lived. Root pressure resulting from osmosis may be 
measured. 
Arrangement of Tissues—The epidermis is pro- 
tective, the wood conducts water to the leaves, and the 
bast and cortex respectively, proteins and_ carbo- 
hydrates from the leaves. The endodermis surrounds 
