Fig. 98 Laminariaceae. A-F, portions of the stipe of Macrocystis 

 passing successively from the epidermiSj A, through the medulla, 

 B-E, to the pith, F. h =hypha, v = connecting thread, t = 'trumpet' 

 hyphae. G, stages in development of mucilage canals, L. cloustoni. 

 H, mucilage canal of L. cloustoni in transverse section. c= canal, 

 5= secretory cells. I, mucilage canal system in L. Cloustoni. c = 

 canal, 5= secretory cells. (After Oltmanns.) 



develops on each side, both callus and sieve plate being traversed 

 by protoplasmic strands. It will be seen that in many respects these 

 trumpet hyphae resemble the sieve tubes of the flowering plants, 

 but although the callus is said to be formed in land plants because 

 of changes in pH, so far no evidence has been published to indicate 

 whether this is also true for the Laminariaceae. Apart from the 

 sieve plates the trumpet hyphae also possess spiral thickenings 

 which appear as striations, and here again there is the problem of 

 their interpretation (e.g. are they growth zones?), although it is 

 possible that they have now lost any function they once possessed. 

 The problem of these trumpet hyphae is still subject to consider- 

 able speculation : it has been suggested that they may be a storage 

 or conducting tissue, whilst another suggested function is that of 

 support, but as the plants are commonly submerged the water 



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