just as the producers of the silver white tubercles in Isopyniin bitcrnatum 

 which, according to MacDougaP develop extensively in soils free 

 from nitrates. On the other hand, the recent investigations of Bjorkenheim- 

 seem to prove that a fungus is concerned in alders. 



In antagonistic symbiosis, dc Bary has used the expression saprophytism 

 and Johow in 1889 defined the idea more closely by distinguishing holo- 

 saprophytcs (those lacking chlorophyll) from hcuiisoprophytcs (those con- 

 taining chlorophyll). 



P>ischoff has contrasted with this the conception of parasitism. Ac- 

 cording to Sarauw^ the expression "parasite" was brought into use in 1729 

 by Micheli for the Balanophoreae*. In agreement with the classification of 

 the saprophytes, Sarauw has distinguished holo parasites (those without 

 chlorophyll) from hcmiparasifes (those provided with chlorophyll). 



Saprophytism is the ability of an organism to take its nourishment from 

 decomposing organic substances, while the parasite drav/s nourishment from 

 the living organism. If we test this classification, based on the forms of 

 nutrition, we find that here, as in all branches of science, a sharp systematic 

 subdivision is assumed only by representatives of a young school, while those 

 of the older and more experienced school are convinced that transition forms 

 exist between the dififerent groups. 



If relative adjacency be compared with iiulriciit association (symbiosis) 

 each forest and each grain field shows how constantly one organism influences 

 the other, according to whether the one leaves any food materials, water and 

 light, for the other. Just as spacial separation sets no fixed limitation to the 

 form of nutrition, the sub-division of the organisms into those with purely 

 mineral nutrition and those dependent on organic substances should be 

 abolished. 



Although plants suited for independent self-nourishment can draw their 

 nutrient material from purely mineral substrata, yet the process actually 

 present consists in their taking humus substances which furnish the food 

 materials in an easily absorbable form because of the activity of a rich bac- 

 terial flora in the soil. The advantages of supplying our fields with animal 

 manures should be thought of in this connection. 



Modern views have strongly modified this distinction between sapro- 

 phytism and parasitism, since they have brought forward numerous exam- 

 ples showing that the organisms called obligate parasites may become de- 

 pendent on saprophytic nutrition in definite developmental phases and con- 

 versely that saprophytes in many instances can assume the parasitic mode of 

 feeding. Miyoshi's^ investigations give us a clear insight into the way 



1 Minnesota Botanical Studies 1894. 



2 Bjorkenheim, Beitrlige zur Kenntnis des Pilzes in den Wurzelanschwellungen 

 von AInus incana. Zeitschr. f. Pflkr. 1904. p. 129. 



:■> Sarauw, G. F. L., Rodsymbiose eg Mykorrlizer saerlig hos Skovtraerne. Botan- 

 isk Tidsskrift 1893. Parts 3 and 4. 



■i But Tournefort in Mem. Ac. Paris 1705, p. 332, speaks of plants which grow on 

 other plants. 



5 Miyoshi, Manaba, Ueber Chemotropismus der Pilze. Bot. Zeit. LII, 1894, pp. 

 1-27. 



