POTASH FROM KELP. 35 
more destructive as the temperature of the water increases, it may 
be an important factor in limiting the distribution of kelp. 
As is the case with all bacterial disease, liability of the plants to 
attack is conditional, to a great extent, upon exposure to the organ- 
isms and upon the number of organisms present. Since the organ- 
ism is very effective only on the surface of the water, plants held 
under water by currents escape. Severe weathering also affords 
considerable protection by removing diseased portions. Thorough 
periodic harvesting is especially beneficial in that it removes all 
diseased portions. “The season for preventive cutting is dependent 
upon a number of factors. The disease is equally effective, ap- 
parently, in heavily matted and in rather open kelp. The tempera- 
ture of the water and the amount of wind and current are prob- 
ably thé important factors. One cutting in May or June might suf- 
fice for a well-exposed bed. whereas, in a quiet sheltered place, a bed 
ES 
o a = = 5 = 
Sie sitt po Sees ae a rags 
Fic. 16.—Shews a more advanced stage of the disease; 
the blade is black. the stipe and remaining cysts dis- 
colored, and the epidermal layer destroyed in spots, 
exposing the colorless tissue beneath. One cyst has 
already sloughed off. 
would probably need to be cut first in March or April and again in 
June or early in July. When the disease appears in a bed that bed 
should be thoroughly cut over as speedily as possible. 
METHODS AND EFFECTS OF HARVESTING AND YIELDS. 
A number of methods of harvesting have been employed, the most 
primitive of which is to gather the kelp as it is washed up on the 
beaches. This method is the least efficient of all, because so much 
material is Jost by sinking and by coming ashore in inaccessible 
places. A second method is to pull up clumps of fronds by means 
of acable and hoist. This method uproots and destroys many plants. 
Fortunately it is more difficult and expensive than cutting and has 
not been employed to any great extent by commercial harvesters. 
The third method, the one usually employed by the so-called hand- 
pickers, is to drag fronds into a skiff or small barge by means of a 
boat hook, and cut them off with a long knife, as far down in the 
water as is convenient. By this method the plants are left in place 
to send up more fronds and all the kelp cut. is saved. Too much 
hand work is required, however, to make it practicable on a large 
scale. 
