POTASH FROM KELP. Si 
If one of these leaves is more carefully examined it will be found to 
taper at the base to a short, cylindrical stem or stipe, the tapering 
base appearing to consist of much younger and more tender tissue 
than the stipe below or the remainder of the blade above. The teeth 
along its margin are also smaller and much more closely set. This 
part of the leaf is the region of most active growth, and might be 
called the “ bud ” of the plant. | 
The tip of the leaf is con- 
stantly dying back and wear- 
ing away. If the leaf is fairly 
large a median cleft or split 
runs through the growing 
region and down into the stipe. 
This cleft is formed by the 
following process: The mid- 
dle layer of the leaf dissolves 
into mucilage, and the outer 
layers sink in to form a groove 
on each face of the leaf; the 
layers of cells under the epi- 
dermis then grow very rap- 
idly, filling up the central cav- 
ity and stretching the epider- 
mis until the whipping action 
of the water splits the leaf; 
the rapidly growing tissue 
then closes the wounds and 
forms a new epidermis over 
the scars. (Wells, 70.) Rap.- 
idly growing tissue like this is 
very susceptible to the action 
of any destructive agency, 
chemical or physical. After 
the initial cleft has been 
formed and the wounds have 
healed, the two separate parts 
of the leaf base continue to 
grow, and finally become sepa- 
rate leaves, the tip being torn 
by weathering. The divided 
upper portion of the stipe also 
lengthens a little, so that each 
new leaf has its own stipe. 
Each new leaf may repeat: _ f 
the process until a cluster "'™ Ns ene Pee ee 
of closely similar, — short- 
stemmed leaves is formed. This is the only way by which Macrocystis 
produces basal leaves or fronds. 
The manner in which a frond arises is somewhat different from 
that in which new basal leaves are formed. The leaf to undergo meta- 
morphosis becomes broader than the other basal leaves and one 
margin grows thick and cordlike. The thickened margin ceases to 
produce teeth. The cleft appears in this case and runs diagonally 
56751—23-_3 
