204 



FORMATIONS AND GUILDS 



[Part II 



and the lauraceous genus Cassytha — both leafless twiners with haustoria 

 on their stems and more (Cuscuta) or less (Cassytha) poor in chloro- 

 phyll. Others again have the habitat of true epiphytes ; such are the 

 mistletoe (Viscum album), Loranthus europaeus and numerous other 

 Loranthaceae, also several Santalaceae of extra-tropical South America. 

 These epiphytic forms are all hemiparasites except Loranthus aphyllus l . 



Many are at the same 

 time climbers. Finally, 

 a separate oecological po- 

 sition may be assigned to 

 those forms that, except 

 for their organs of repro- 

 duction, are buried within 

 their host. 



In the case of fungi, still 

 greater differences in their 

 mode of life exist ; for one 

 reason, because they, un- 

 like phanerogams, are not 

 confined to vegetable sub- 

 strata but also attack 

 animals, and also because 

 many species assume dif- 

 ferent forms on different 

 hosts. 



Like saprophytes, para- 

 sites belong to a relatively 

 small number of sys- 

 tematic groups, and are 

 most numerous among 

 fungi and bacteria. Algae 

 include only a few holo- 

 parasites compared with 

 the more numerous hemi- 

 parasites in the group. 

 Holoparasites and holosa- 

 prophytes alike are want- 

 ing among mosses, pteridophytes, and gymnosperms. The analogy 

 between the two oecological groups of holoparasites and holosaprophytes 

 does not extend to angiosperms. Although there is a parasite (Melampy- 

 rum pratense) that apparently can also exist saprophytically (L. Koch), 

 yet the two modes of organic nutrition among angiosperms are systemati- 



1 According to Johow. 



Fig. 112. Cuscuta europaea. In the centre a willow twig 

 round which the parasite is twining, b reduced leaves, Bl 

 flowers. On the left, connexion of the parasite Cits with its 

 host IV. H haustoria. v, c, s vascular bundle of the host. 

 On the right, seedlings ; t base of seedling dying off. From 

 Strasburger's Text-book of Botany. 



