PARASITES AND SAPROPHYTES. 367 



the second as Coprophytes or Saprophytes. The comparative insignificance of this 

 distinction, if the aim of nutrition is exclusively kept in view, is seen at once from the 

 fact that some Fungi which are usually parasitic can grow in artificially prepared 

 nutritive solutions — e. g. Agaricus mellcus. Several species of Mucor again are able 

 to obtain nutriment for their mycelium from the tissues of fresh Apples, although they 

 also flourish in saccharine nutritive solutions or in gelatine. The main fact is simply 

 that plants devoid of chlorophyll are necessitated and are able to absorb their car- 

 bonaceous substance from without in the form of organic compounds. This how- 

 ever by no means excludes the fact that in general each individual species is met 

 with in the natural course of things only as a parasite or only as a saprophyte, and 

 that very often the most capricious choice of nourishing substratum is exerted in the 

 matter. Most parasites flourish only on perfectly definite species of other plants or 

 animals ; nay, many of them, particularly parasitic Fungi, can only enter into 

 perfectly definite parts of their host-plant. Even saprophytes hit upon a careful 

 choice of their substratum. It also happens, it is true, that certain parasites settle on 

 the most various host-plants and some saprophytes inhabit any substratum whatever. 

 It is evident that biological points here come into eff"ect which are connected not 

 directly and exclusively with nutrition, but with other physiological properties of the 

 plant in addition. 



Although plants which contain very little or no chlorophyll are necessarily para- 

 sites or saprophytes, it by no means follows that all parasites must be devoid of 

 chlorophyll. I have already had occasion in Lecture III to mention the Loranthacese, 

 which abound in chlorophyll and are nevertheless parasitic ; particularly the Miseltoe. 

 In such cases the parasite really needs to absorb from the host-plant only water and 

 mineral substances dissolved in it, though it is not excluded that certain organic 

 compounds of the host-plant may possibly be indispensable to the parasite in very 

 small quantities. Plants which contain chlorophyll also occur among the sapro- 

 phytes, as Neottia Nidus-avis, Corallorrhiza, etc. in the family of Orchidese ^ where at 

 least the flowering-stems which project above the surface of the soil contain chloro- 

 phyll, of course in quantities so small, and appearing so late in the life of the 

 plant, that it comes into consideration for the total process of nutrition just as little 

 as does the chlorophyll developed under the peel of a potato lying in the light for 

 the development of the tuber. 



I have also already spoken in Lecture III of the parasitism of Thesiian and 

 RInnanthus. These green-leafed plants develope a somewhat richly branched system 

 of roots in the earth, single threads of which become united by means of small 

 haustoria with the roots of neighbouring plants containing abundance of chlorophyll. 

 It is not yet known, however, how far this partial parasitism is of importance for the 

 life of these plants. 



The most remarkable case of supplementary nutrition in plants containing 

 chlorophyll, by the absorption of organic substance, is offered, finally, by the 

 so-called insectivorous or carnivorous plants, to which I shall return in detail 

 further on. 



We will, first, once more regard the processes in parasites and saprophytes 



' Drude, 'Die Biologie der Monotropa Hypopitys und Neoltia' ^Göttingen, 1S73), pp. 32, 33. 



