640 THE PATHOeENIC ALGAE. 



The lichen-symbiosis is the most marked example of mutual 

 symbiosis we know. Amongst the partnerships of Algae with 

 animals every form exists from mutual symbiosis to true 

 parasitism or to typical epiphytism. The last condition is, how- 

 ever, more frequently met with amongst Algae or Lichens 

 epiphytic on other chlorophyllous plants. The phenomenon 

 of " shelter-parasitism " is also a frequent one, the Algae 

 inhabiting cavities already present in the host, or " domatia " 

 — places of abode formed with the assistance of the Algae. 



The full discussion of these and other symbiotic relationships 

 may be had by reference to the works dealing with subject; 

 some of the more important of these are given: 



De Bary, Die Ehscheinung der Symbiose, 1879. 



O. Hertwig, Die Symhiose im, Thierreich, 1883. 



Klebs, " Symbiose ungleichartiger Organismen.'' Biolog. Centralblatt, 

 1882. 



Klebs, " Beitrage zur Kenntniss niederer Algenformen," Botan. Zeitung, 

 1881. 



Geza Entz, " Das Koiisortialverhaltniss vou Algen und Thieren," Biolog. 

 Centralblatt, 1882. 



Brandt, " Die morphologische und physiologische Bedeutung des Chloro- 

 phylls bei Thieren.'' Mitiheil. d. Zoolog. Station Neapel., 1883. 



Van Beneden, Animal parasites and Messmates. (English Edition), 

 International Scientific Series. 



Only these algae which are parasitic on the higher plants 

 come, strictly speaking, within the limits of the present work; 

 we shall, however, also take into consideration the interesting 

 symbiotic adaptations presented by several algae which live 

 endophytic, but not truly parasitic, in higher plants.^ 



There is a distinct resemblance between the parasitism of 

 algae and that of parasitic fungi. Some parasitic algae live 

 in the intercellular spaces of their host, others inside the 

 host's cells, and many of them inhabit algae and other aquatic 

 plants. A large number of algae live as eudophytes, many 

 of them in cavities occurring naturally in other plants ; such 

 we can hardly regard as parasites ; nor those which cause the 

 formation of " domatia " on their hosts, since these structures 

 are an indication of a symbiotic rather than of a parasitic 



'Altmann (Botan. Zeitung, 1894, p. 207) describes a number of marine algae 

 parasitic on Facaceae ; Moebius, " Endophyte Algen," Biolog. Centralblatt, 1891 ; 

 also Conipectus olgarum endophytamm, etc., 1891, with complete bibliography. 



