54 BULLETIN 150, U. S. DEPARTMENT OF AGRICULTURE. 
surface, from the enlarged portion of the stipe upward, 
has an important bearing on the harvesting of this species, as cut- 
ting the stipe a few feet below the surface severs practically the entire 
plant. 
The Macrocystis, a perennial, reaches an average length of 100 feet 
and grows likewise in regions favored by a rocky bottom and a swift 
tideway or heavy surf. It attaches itself in the same manner as does 
the Nereocystis — which is characteristic of the kelps — but instead of 
a single stipe extending from the holdfast it develops a number, 
which give the effect of a bushy or branching plant. The fronds are 
distributed along the entire length of the stipe. These reach a maxi- 
mum of about 3 feet in length and decrease in size as the upper or 
younger end of the plant is approached. A short section of stem 
connects the frond to the stipe and bears a pear-shaped enlargement, 
which is hollow and serves as the pneumatocyst. The plant does not 
stop growing on reaching the surface, but a large portion of its length 
lies upon the surface, supported by its numerous pneumatocj^sts, and 
trails out in the tidal currents. 
Reproduction by these species is by means of sporangia, small 
bodies which develop on the fronds, in the case of the Macrocystis on 
the old fronds near the bottom, and which are thrown off to find 
lodgment and develop into new plants. As the Nereocystis is in 
effect an annual, its continuance is dependent on annual reseeding. 
While plants have been observed which have withstood the 'winter's 
cold and storms, thus appearing to be at least a biennial, most of the 
groves are torn out by storms during the winter and re-formed dur- 
ing the following summer. In harvesting these groves, then, due 
precautions must be taken to leave enough plants for resporing, or 
to postpone harvesting until after the sporing season. In the case 
of the Macrocystis it is probable that no such precautions need be 
observed. 
In this connection it should be said further that only one harvest- 
ing per season of the Nereocystis is possible, since cutting that plant 
a few feet below the surface of the water, as pointed out, severs the 
entire growing portion. It is necessary, then, to await the new 
growth of the next season. 
Such is not the case with the Macrocystis. Cutting that plant a 
few feet below the surface of the water severs only the upper part 
of the growing portion, possibly one-half, and does not kill the plant. 
On the contrary, there seems to be a certain stimulation in growth 
exhibited by a sort of "stooling" effect; while the old stipes slowly 
decay, fresh shoots appear, resulting in a thicker growth. It is esti- 
mated that after a cutting, a grove resumes its original condition 
after a lapse, of 40 to 60 days. 
