THE NUTRITION OF HETEROTROPHIC PLANTS 177 



[NiKLEWSKi. 1905. Beih. z. bot. Centrbl. 19, i.] 



Pfeffer. 1872. Jahrb. f. wiss. Bot. 8, 485. 



Pfeffer. 1873. Monatsber. Berl. Akad. 



Pfeffer. 1892. Stud, zur Energetik, Abh. SSchs. Gesell. 18, 275. 



[Prianischnikow. 1904. Ber. d. bot. Gesell. 22, 35.] 



Ramann, E. 1898. Zeitschr. f. Forst- u. Jagdwesen, Rev. Bot. Ztg. 56 231. 



Schimper. 1885. Bot. Ztg. 43, 756. 



ScHULZE, E. 1898. Zeitschr. f. physiol. Chem. 24, 18 ; ibid. 30, 241. 



Strasburger. 1891. Bau u. Verrichtung d. Leitungsbahnen. Jena. 



De Vries. 1885. Bot. Ztg. 43. I- 



[Wachter. 1905. Jahrb. f. wiss. Bot. 41, 165.] 



[Weevers. 1904. Jahrb. f, wiss. Bot. 39, 229.] 



Wehmer. 1892. Landw. Jahrbiicher 21, 513. 



WORTMANN. 1890. Bot. Ztg. 48, 58 1. 



LECTURE XV 



THE ACQUISITION OF CARBON AND NITROGEN BY 

 HETEROTROPHIC PLANTS 



We shall now leave autotrophic plants and turn to the consideration of 

 heterotrophic forms, that is to say, forms which have no power of forming carbo- 

 hydrate from carbon- dioxide, nor the capacity for building up proteid out of 

 nitrates or ammonia. They are dependent on previously manufactured organic 

 substance, and also, in nature, on the nutriment they are able to take from other 

 and autotrophic plants. In reality the contrast is not so sharply defined as 

 it appears. In the first place, so far as the acquisition of carbon is concerned, 

 only certain definite cells in autotrophic plants are really autotrophic, i. e. those 

 which contain chlorophyll, all others are actually heterotrophic. We have seen 

 that all subterranean organs, even the aerial stem itself, all growing regions 

 and growing points, embryos, &c., are entirely dependent on already con- 

 structed organic substances. It may be further noted that the foliage leaf 

 even, the specific organ for autotrophic nutrition, may, under certain 

 conditions, be constructed exclusively out of carbohydrates, &c., brought to 

 it from without (JosT, 1895). Although it is impossible in general to nourish 

 higher plants in a purely heterotrophic manner in the absence of carbon- 

 dioxide, the reason lies rather in the purely experimental difficulty of 

 the research than in the natural and fundamental difficulties of the case. 

 In some cases (Laurent, 1898) these difficulties may be overcome. [Laurent 

 has shown in a recently published work (1904) that in the case of maize seed- 

 lings fed on sugar in the dark, the increase in weight always remains quite 

 small] Typical autotrophic plants in nature certainly live on carbohydrates 

 manufactured by themselves, but there are also nontypical forms which, 

 according to external conditions, are able to exist either in an autotrophic or 

 heterotrophic manner {Euglena : Zumstein, 1899). [Artari (1899 and 1904) 

 showed that the growth of certain lower Algae could be furthered by adding 

 sugar.] 



Since, then, the contrast between autotrophic and heterotrophic organisms 

 is not so fundamental as it at first appears, we need not expect to find any 

 entirely new feature in the nutrition and metabolism of heterotrophic plants. 

 At the same time it is the proper course for us to devote a special section to the 

 treatment of heterotrophic plants, since they exhibit in many respects peculiar 

 conditions of life, and are much better adapted for the study of many problems 

 in nutrition than are autotrophic plants. 



Not infrequently the plant exhibits many diagnostic characters both in 

 form and in mode of life which serve as criteria for determining whether it is 



TOST N 



