POTASH FROM KELP. 29 
a grove is given in the tables, although that grove may not have 
been entirely cut over in any given month; but, on the other hand, 
the areas of certain other groves are omitted as not having been cut 
over at all, it being the custom of most harvesters to cut the same 
portions of a kelp bed two or more times in a month and leave 
other beds uncut, either because they are not considered worth cut- 
ting or because of unfavorable weather or distance. 
‘The great reduction in yield per unit area in the summer months 
is due in part to the cutting of thin groves which have been passed 
by in the winter, when kelp was plentiful and cutting difficult and 
_ dangerous. 
| Sporulation or fruiting of Macrocystis, like growth, is practically 
continuous throughout the year. but varies in amount with the sea- 
sons. Unlike the floating fronds, the fruiting leaves escape the de- 
one effects of storms, as they are borne near the base of the 
plant. 
In the dormant season the fruiting areas are reduced to small 
patches on a few of the fertile leaves, or sporophyls, at the base of 
the plant, but in the middle of the growing season practically the 
whole area of every sporophyl is pressed into service. Vertical hauls 
from bottcm to surface made at the edges of a kelp bed, with a tow- 
ing net of No. 25 bolting silk, revealed the greatest number of free 
swimming spores in the autumn. This fact, however, does not indi- 
cate that there is less spore production in winter than in autumn, 
since the spores produced in winter appear to settle much more 
quickly. Bim 
As to the fruit itself, the spore-producing areas are not restricted 
to grooves. Their appearing to be so is due to their being worn 
away from the ridges of corrugated sporophyls. The thousands 
of fruiting leaves that have been examined have shown both per- 
fectly plane and deeply corrugated surfaces. 
~ In the summer the sori are restricted to small, irregularly rounded 
blotches, but in winter they completely cover the sporophyis develop- 
ing from the base as the sporophyls at the tip liberate their spores 
and disintegrate. The sori occur as thickened, opaque areas, richly 
colored and soft in texture. 
DESTRUCTION BY NATURAL AGENCIES. 
In addition to the normal thinning of kelp beds in summer by 
deterioration, disappearance of old material, and decreased growth, 
entire kelp beds sometimes disappear. Sometimes this extensive 
disappearance is due to decay unaccompanied by regeneration. In 
the vicinity, of Santa Barbara, heavily matted kelp beds have been 
known to sink and not reappear for months. Several beds disap- 
peared in that way in July, 1917. Many persons claim that kelp 
beds in that vicinity have disappeared similarly in the past, but 
since the reports do not agree as to time, they can not be used as 
data. The 1917 sinkings were not studied closely enough to yield 
any but theoretical explanations. The immediate cause of such 
sinking could readily be overlooked because a current not visible 
from shore might completely submerge a kelp bed for several days 
ata time. 
