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10 BULLETIN 1191, U. S. DEPARTMENT OF AGRICULTURE. 
the manner of a clump of mint. This spreading habit of one type 
of Macrocystis will be referred to later in this bulletin. Many of 
the basal leaves of this specimen fruited in midwinter, but no fruit 
was seen in May. 
YOUNG PLANTS. 
In addition to the observations at San Pedro, careful watch for 
young plants was kept in various kelp beds and on several beaches. 
Plants with only one-or two fronds, and these with rather slender 
stipes, thin-walled cysts, and rather delicate leaves such as one would 
naturally expect young plants to have, are rarely seen in kelp beds. 
No changes take place in the appearance of a kelp bed by which one 
can recognize the coming in of a new generation. 
At more or less irregular periods, but chiefly in spring and early 
summer, young plants come in on the beaches in fairly large num- 
bers, though not at all comparably to the young Nereocystis plants 
that come in on northern California beaches in midsummer. In 
May, 1919, these young plants appeared in greater number on the 
beach at La Jolla than at any other time or place considered in this 
bulletin. Many of these could be readily untangled, and were suffi- 
ciently well preserved for measurement. About 400 of these plants 
were collected and measured for the purpose of finding the rate of 
growth. The work was discontinued because many young plants of 
considerable size were soon found that could not be untangled from 
the masses of seaweed without breaking, but which would have had 
to be used in order to get results of real value. During May more 
than 400 plants were measured, having an average length of 3 feet. 
These regularly had 2 fronds, 2 narrow leaves between the fronds, 
a slender primary stipe about 4 inches long, and a flat holdfast 
about 2 inches wide. ‘The development of the holdfast and the size 
of other parts indicated that they had grown at four or five times 
the rate of the plants observed at San Pedro. 
In addition to these plants, there were others measuring 15 to 20 
feet in length. These had their third and fourth fronds well started 
and the holdfast better developed than in the young plants, but 
were apparently not more than 7 or 8 months old. On the other 
hand, very small plants were often found. Some of these were 
attached to the holdfast of larger young plants, or had grown up 
so close beside them as to let go and drift ashore with them. Other 
examples were found of young plants having started on old stems 
of seaweeds, which had broken off and come ashore with them. One 
old stipe, apparently Egregia, less than 2 feet long, had more than 
a dozen young plants attached to it. The smallest plants thus were 
only 0.2 inch long. These had already formed a stipe, but there 
appeared to be but little expansion at the base. The blade was very 
thin and perfectly plane, with a smooth, entire margin. These tiny 
plants all had the tip more or less worn off. Macrocystis plants 
can hardly be distinguished from Egregia or other young kelps, 
especially when they come in with most of their color faded out. 
Among the drift plants they were regarded as Macrocystis because of 
having come from too great a depth for shore kelps. On San Pedro 
breakwater it is not easy to identify Macrocystis before the grooves 
for the first split begin to appear, because of the great quantity of 
