180 Sir Everard Home on the changes the blood 
tion of wheat, introductory to his illustrations of the diseases in 
corn, he sowed a quantity of w r heat, and afterwards took up 
every day some grains, or plants, for examination, till the 
ears were ripe. In his close attention to the changes that 
took place, he was very much struck with the rapid increase 
of the tubular hair of the root of a young plant of wheat, in 
its earliest stage of vegetation : and fixing his whole attention 
upon that part of the plant, he observed small pustules of a 
slimy substance arising under the epidermis, on the surface 
of the young root ; and, in a few seconds, a small bubble of 
gas burst from the root into the slimy matter, which it extended 
in a moment to the length the hair was to acquire ; and 
the slimy matter, surrounding the gas, immediately coagu- 
lated, and formed a canal. He repeated his observations on 
another plant, whose pubescence consisted of a jointed hair, 
and observed the same effect take place ; a bubble issued 
from the young stalk, and extended the slimy mucus to a 
short distance, forming the first joint, which immediately 
coagulated and became transparent, and at its extremity a 
new pustule of the same slimy mucus accumulated, into 
which, in a short time, the gas from the first joint rushed ; 
and thus, in a moment, a second joint was formed : in the 
same manner he observed the formation of the hairs of ten 
or twelve joints to take place. 
These observations, so curious in themselves, and which 
explain, in so simple and satisfactory a manner, one of the 
modes in which tubes are formed in vegetables, and an addi- 
tion is made to the plant, made so strong an impression on 
my mind, and so entirely engrossed my attention, that I did 
