EUPHYCOPHYTA I9I 



which each branch becomes strap-shaped and bears three types of 

 outgrowth : 



(a) Ligulate sterile outgrowths. 



(b) Small fertile outgrowths. 



(c) Conspicuous stipitate bladders. 



Recent work has shown that in deep-water plants most of the 

 bladders contain Uquid rather than air and therefore cannot func- 

 tion as flotation organs. The shape of the lower bladders is related 

 to the depth of water in which the plant is growing. 



The female gametophyte is composed of one or two large cells 

 whilst the male plant is composed of numerous smaller ones, both 

 plants reaching maturity in from nineteen days to four weeks de- 

 pending on the season of the year, e.g. the length of dayhght. 

 Maturity is most rapidly reached at a temperature of io-i6° C, 

 and although at 16-20° C. gamete development takes place never- 

 theless the antherozoids are unable to leave the antheridia. 



REFERENCES 



Lamtnarta 



Kuznetzovj V. V. (1946). Comt. Rend. Acad, Set. U.R.S.S., 36 (6), 



533. 

 Parke, M. (1948). J. Mar. Biol. Ass. U.K.y 27, 706. 



Macrocystis 



Papenfuss, G. F. (1942). Amer.J. Bot.y 29 (i), 15. 



Sargent, M. C. and Lantrip, L. W. (1952). Amer.J. Bot., 39 (2), 99- 



* FUCALES 



The sporophytic plants are even more dominant in the Ufe cycle 

 than in the Laminariales, but although diploid there is no apparent 

 asexual reproduction, the plants always reproducing by means of 

 ova and antherozoids. In most genera it is Hkely that the plants 

 exist over more than one season : this has been clearly established 

 for species of Fucus^ Ascophyllum, Durvillea and Marginariella 

 urvilliana. There is considerable tissue differentiation, and in their 

 external features the plants exhibit much more variation than is to 

 be found in the Laminariales. The thallus is normally differentiated 



