LAMINARIALES (HETEROGENERATAE) 171 



which can vary greatly in form. The simplest transition area from 

 stipe to lamina is quite plain, but one may also find folds, ribs or 

 callosities in that position, which is also the region of intercalary 

 growth. Laminaria Sinclairii has been studied by Setchell (1905) in 

 some detail in connexion with regeneration, a common feature 

 throughout the genus. Three types of growth can be recognized, all 

 of them confined to the stipe, whilst it is also possible to find all 

 three processes taking place in one individual : 



(i) The ordinary growth and extension of the blade during the 

 growing season. This hardly merits the description of continuous 

 physiological regeneration given to it by Setchell unless the concept 

 of regeneration is to have a wider significance. 



(2) Periodic physiological regeneration which represents the 

 annual process whereby the new blade is formed. The transition 

 area bulges, due to new growth in the medulla and inner cortex, and 

 then ruptures from the pressure, thus leaving the frayed ends of the 

 non-growing outer cortex forming collars, the upper one of which 

 rapidly wears away. After the rupture the new cells of the medulla 

 and inner cortex elongate rapidly. The failure of the outer cortex to 

 grow is probably associated with the proximity of the inner cortical 

 cells to the medullary hyphae where they can monopolize all the 

 growing materials, thus cutting oflF any supply to the outer cortex, 

 but there may, of course, be other factors involved. 



(3) Restorative regeneration whereby branches arise from 

 wounded surfaces, the same tissues being involved as in process 



(2)(cf. fig. 115). 



Many of the species are used as food by the Russians, Chinese 

 and Japanese. In Japan, foods derived from about ten different 

 species of these algae are known as Kombu, kelp gathering from 

 July to October forming quite a big industry. Goitre is practically 

 unknown in Japan, and its absence must be largely connected with 

 the iodine obtained from this algal food. Here we have an ex- 

 ample of a region where the absence of a disease can be directly 

 associated with the presence and nature of a particular kind of food. 

 Apart from food the kelps are generally employed as a source of 

 iodine and also as fertilizers. 



The following brief notes concern a few species that are of more 



general interest: 



L. Cloustoni. The attachment crampons are arranged in four 



