Holdfast morphology of Macrocystis spp. 

 (redrawn from Neushul 1971a) 



-haptera ^-^T~>^ 



WAM^&t 



M. pyrifera M. angustifolia M. integrif olia 



holdfast 



Morphology and life history of M. pyrifera 

 (modified from Dawson and Foster 1982) 



blade with 

 sorus 

 (sporophyl !).■;'_" 



frond 



sporangium (2N) 



. zoospore (N) 



r) x p s young 



gametophytes 



antheridia 



<$ gametophyte 

 CN) 



macroscopic 



adult 



sporophyte 

 diploid (2N) 



embryonic 



sporophyte 



(2N) 



fertilization 



oogonium 



O gametophyte 

 * CN] 



microscopic 



juvenile 



sporophyte 



(2N) 



Figure 1. The morphology and life history of Macrocystis . 



Dense stands of Macrocystis provide a 

 vertically-structured habitat through the 

 water column, and may have a considerable 

 shading effect on the organisms below. 

 These stands also provide nurseries, feed- 

 ing grounds and/or protective cover for 

 many other organisms. Darwin (1860) 

 referred to them as great aquatic forests 

 of the southern hemisphere, comparing them 

 in complexity to terrestrial forests. 

 Thus, giant kelp forests have come to mean 

 the areas of coastline featuring extensive 

 coverage by the surface canopy of 

 Macrocystis . Other kelps (using a re- 



stricted definition of "kelp" as members 

 of the Order Laminariales) that form sur- 

 face canopies in temperate and polar re- 

 gions may also form quite dense forests, 

 but their tissue floating on the surface 

 of the sea tends not to be as extensive as 

 that of Macrocystis (see Section 3.2.2). 

 We will refer in general to communities 

 with surface canopy kelps as "kelp 

 forests," those with primarily Macrocystis 

 as "giant kelp forests," and those with 

 other particular kelps as "bull kelp 

 forests, etc." depending on the genus or 

 species. 



