POTASH FROM KELP. 7 9 
and those dying in the summer is accounted for by the fact that plants 
from autumn spores develop rapidly, whereas those from late-winter 
or early-spring spores make little or no progress at first. Thus, in 
either case, the bulk of the new growth must make its start in autumn 
or early winter. 
The San Pedro breakwater has also furnished interesting data 
regarding phenomena of development of young plants. They start 
first in crevices or small cavities where they are not exposed to the 
full wash of the surf. On the more fully exposed surfaces regenera- 
tion is very slow. The plants that do grow up in exposed situations 
make a much slower growth than those better protected. Protection 
from violent wave action has much the same effect on the general 
appearance of a kelp plant as shading and prctection from wind 
have on a land plant; that is, the protected plant produces a longer 
stipe and much larger, and thinner blades than the exposed plant. 
Plants in exposed places on the breakwater were not more than 1 or 
2 inches high when the better protected plants had a height of 16 to 
18 inches. Kelps took hold more readily where the rocks were 
eovered with barnacles and other small animals, and small seaweeds, 
than where their surfaces were clean. ‘Frequently kelp plants were 
found attached to small red seaweeds. Where conditions are favor- 
able, the young plants start thickly, often standing less than an inch 
apart, the strong ones crowding out the weak as they grow. 
DEVELOPMENT OF HOLDFAST. 
Another very important point observed was the rate of develop- 
ment of the holdfast. The first few whorls of hapteres grow out at 
very short intervals to form a flat holdfast. This holdfast does not 
keep pace with the upper parts of a vigorous young plant, and as a 
result the plant becomes very insecurely anchored. Later on, how- 
ever, when the primary stipe has become stouter and a number of 
fronds have been sent up, numerous stout hapteres bud out higher 
up and securely anchor the plant. 
REGROWTH. 
A plant selected for regeneration experiments behaved in a man- 
ner resembling new plants, as regards seasonal growth. This plant 
was in a slightly protected place, and was a strong specimen with 
a somewhat larger holdfast than most of the plants on the break- 
water had. The fronds were all cut down to a height of 16 to 18 
inches in November. Some new fronds were found growing up in 
December. These began to weather down when 3 or 4 feet long. 
New fronds appeared from time to time, but wore back too rapidly to 
produce much foliage during winter. When visited early in May, 
there were 12 fronds. None of these was more than 7 or 8 feet 
long. On some fronds, 3 or 4 feet long and growing vigorously, the 
lower laterals had already formed clusters of four or more leaves 
each. All fronds found at this time were cut off below the lower- 
most cyst. By the end of May, 6 new fronds had started, of which 
the longest had a length of 3 feet. During the seven months that 
it was under observation, the holdfast of this plant had increased 
from about 1 foot to 2 feet in diameter, and had died in the center, 
showing that the plant has a tendency to spread at the base after 
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