54 BULLETIN 150, U. S. DEPARTMENT OF AGRICULTURE. 



surface, from the enlarged portion of the stipe upward. This fact 

 has an important bearing on the harvesting of this species, as cut- 

 ting the stipe a Jew 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 Xereocystis — 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 pneumatocysts, and 

 trails out in the tidal currents. 



Beprocluction 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 Xereocystis 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 Xereocystis 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. 



