
THE ROOT 67 
through the lateral branches of a root, their mode of origin 
will be seen. 
'The lateral 
roots arise 
opposite the 
groupsof wood, 
and as thereare 
four groups in 
a typical Dico- 
tyledon, the 
lateral branches - 
will be in four 
rows. It must 
be remembered 
that this num- 
ber is not con- 
stant, but it is 
frequent ; the 

: : Fic. 36.—DicoryLEpoNOUSs Root witH LATERAL 
point to notels = Braycu, TRANSVERSE SEcrion. (High power.) 
that the num- pf, pericycle ; 7, lateral root. 
ber of rows of 
branches in a fully-grown root is the same as the number of 
groups of wood in a primary root. In Monocotyledons the 
number of bundles is greater than in a Dicotyledon. ‘The 
branches arise from the pericycle, the cells of which divide, 
giving rise to the growing point of a young root, which 
pushes its way through the outer tissues, the cells on each 
side becoming broken down and gradually absorbed. 
Growth in Lhe root grows in length only just behind its 
Length and apex. As soon as the young meristematic cells 
Sees have grown to their full size they become perma- 
nent tissue, and do not grow any further. | 
Growth in thickness takes place in the older parts of the 
toot owing to the formation of secondary wood and_ bast, 
Which originate from the cambium formed as the root grows. 
In order to see this a series of sections must be made at 
intervals of an inch or two behind the tip. 
