— 
POTASH FROM KELP. 19 
size of the Jaterals. When the water is too warm for vigorous 
growth, some leaves next the tip do not develop. Throughout the 
life-cycle of the frond, all leaves, including the terminal one, 
weather away at the tip. In an old leaf, renewal at the base de- 
creases and finally ceases, but the tip continues to wear away untu 
the blade is reduced to a mere stub on the top of the cyst. Even 
this cyst may rot off. At the same time, animals perforate and 
variously abrade the leaves, thereby hastening their destruction. 
From a combination of causes old fronds may lose the most of their 
leaves. With age the cysts gradually become heavier because of the 
water oozing through their walls, and finally they sink. The added 
weight of small animals and plants which completely cover the 
leaves at times seem to hasten the sinking. Some small encrusting 
animals (Membranipora) form a bony crust on the surface of the 
leaves which makes them unusually brittle, and causes large num- 
bers of them to break off and drift away. Weakening of the tissues 
with age or disease also results in the sloughing of fronds. 
While the main frond has been growing to the surface, attaining 
maturity and decaying, the dividing laterals near the base have 
become clusters of typical sporophyls, which may continue to lib- 
erate spores, even after the upper portion of the frond has rotted 
away. Sometimes the upper laterals when old also develop sori. 
They do not subdivide, however, nor do they continue to grow after 
the fruiting tissue makes its appearance. Such fronds show great 
deterioration at the time of spore liberation. The leaves are worn 
down to half their normal length, the cysts are full of water, and 
the stipes are sometimes so weak as to break when one tries to lift 
the frond. Most of the color is gone, the chestnut-brown sori stand- 
ing out very conspicuously from the straw-colored remainder of 
the frond. 
The life-cycle of a frond, as given above, probably consumes from 
four to seven months, ofwhich time a month or six weeks is required 
to attain the surface of the water. As the old frond deteriorates, a 
fresh one comes up to replace it. 
SUMMARY OF LIFE HISTORY. 
Spores are produced at all times of the year, but plants make 
their best growth from autumn or early-winter spores. 
Spores are sticky and cling firmly to the first object with which 
they come in contact. 
The first stages in the development of the young plant are very 
‘difficult to understand. 
Young plants are not large enough to be readily discerned with- 
out a microscope until they are nearly 3 months old. 
At the age of 6 months young plants are 18 inches tall or taller, 
and are sending up their first two fronds from two growing points. 
At 9 or 10 months a plant is beginning to yield kelp in commercial 
quantities, and is also beginning to fruit. 
After sending up the first two fronds, young plants differentiate 
into three types. The first does not appear to produce more than two 
growing points from which fronds arise; the second branches re- 
peatedly to form a dense bush from which 20 or more fronds may 
