EUPHYCOPHYTA 49 



REFERENCES 



General 



Fritschj F. E. (1935). Structure and Reproduction of the Algae^ Vol. I, 

 pp. 145-98. Camb. Univ. Press. 



Hydrodictyon 



Neeb, O. (1952). Flora, 139 (1)5 39- 



Pirson, A. and Doring, H. (1952). Flora, 139 (2), 3i4- 



Pocock, M. A. (i960). Jowm. 5. Afr. Bot. 26, (3/4), 170. 



Sorensen, I. (1951)- Oikos, 2 (2), 197. 

 Characium 



Starr, R. C. (i953). Bull Torr, Bot. Club, 80 (4), 308. 



* Ulotrichales 



This order comprises filamentous and parenchymatous types 

 which have clearly evolved from the filamentous form. There is 

 little or no differentiation between base and apex in many of the 

 forms though there is commonly a special attachment cell or pad of 

 cells. In most genera all the cells except those for attachment are 

 capable of producing reproductive bodies, but in two genera 

 recently described from New Zealand (Gemina, Lohata) there ap- 

 pears to be a considerable degree of sterihzation. Within the genus 

 Enteromorpha there is also evidence of the development of hetero- 

 trichy or the condition in which the thallus possesses a prostrate 

 adherent portion and an erect aerial portion. 



In the past the treatment of the genera in this order has varied 

 considerably. Some workers have divided the genera into three 

 orders, Ulotrichales, Ulvales and Schizogoniales or Prasiolales. 

 Others have recognized only the first and last of these orders, or 

 else have regarded them as forming two suborders, the Ulotri- 

 chineae and Prasiolineae. Even when only one order is recognized 

 some authorities accept only three famiUes (Ulotrichaceae, Ulva- 

 ceae and Prasiolaceae) whereas others believe that there should be 

 as many as eight families. 



* Ulotrichaceae: Ulothrix {ulo, shaggy; thrix, hair). Figs. 23, 26 



The unbranched filaments are attached to the substrate by means 

 of a modified basal cell which frequently lacks chlorophyll, but 

 even though attached at first, the plants may later become free- 

 floating. Under unfavourable conditions, e.g. lack of nutrients. 



