I'lisifonu, 2-2|- inches long, afterwards becoming clavate, and then cylin- 

 drical, and eventually 4-5 inches or more in length. Substance of the 

 young leaves membranous, of tlie old coriaceous. In drying it does not 

 adhere to paper. 



We here figure one of the many varieties of the great "Kelp " 

 of the Southern and Pacific Oceans, said to be the longest 

 (though not the largest) vegetable in the world. The cord-like 

 stems, when the plant grows in deep water, have been estimated 

 variously at 500 and at 1,500 feet. A middle number would 

 probably be no exaggeration ; though ofi' the Australian coast 

 no such length has been ascertained. At whatever depth the 

 plants vegetate the stem rises, at a considerable divergence from 

 the perpendicular, to the surface, where its leaves are buoyed up 

 by their vesicles, and it often stretches along the waves for many 

 fathoms horizontally. 



The mode of development of the new leaves — by a splitting 

 in the base of the terminal leaf — is better shown by our Fig. 2 

 than can be explained by description. It is only the terminal 

 leaf, which must be regarded as a modification of a " bud," 

 which developes new leaves ; the lateral leaves, once formed, 

 remain unchanged till they decay. 



I still adhere to the opinion, expressed many years ago, that 

 the various forms of Macrocystis, which many authors regard as 

 " species," are merely varieties, dependent on local circumstances, 

 or on age, etc. 



Fig. 1. Apex of a stem of Macrocystis, showing the teripinal primary leaf, out of 

 which the lateral leaves are successively formed by continual vertically as- 

 cending splitting of the base. 2. Portion of the older stem, with adult 

 leaf aud vesicles : — both figures the natural size. 



