96 



SVMI'.lusls. 



in 3fi>/inf<-/i<t. The root-system of a tree has not only to secure 

 nourishment, but also the rigidity and stability of the tree. 1 

 This latter can only be attained by a wide distribution of roots 

 in the firm subsoil free from humus, where normal roots with 

 root-hairs will be formed. The nursing function of the mycorhiza 

 seems thus to be less important than in the case of 



FIG. IS. Mycorhiza of Pinus '',<'<<. A, Typical mycorhiza. B, Root showing 

 clusters of mycorhiza as well as portions clad with fine root-hairs. C, Rootlet 

 exhibiting button-like thickenings externally devoid of a fungoid mantle, but 

 internally completely destroyed by mycelium. D, Section through a thickened 

 branch of a mycorhiza-cluster : a, fungoid mantle ; l>, fungoid tissue between 

 the cells of the root, rendering them unrecognizable except by their large nuclei ; 

 the inner parts contain no fungi, (v. Tubeuf del.) 



My newest investigations on this subject 2 show that, amongst 

 the gymnospermous forest-trees, the Abietineae alone have roots 

 externally clothed with a fungus ; the remaining groups have 

 all endophytic mycorhiza. The Abietineae have frequently only 

 a tine mantle of fungus on their rootlets, and do not produce the 

 tufts of short, branched roots so characteristic of mycorhiza in 

 general. Frank does not seem to be altogether correct in his 

 view that the Abietineae are almost or quite incapable of multi- 

 plication by slips, because they would then require to exist for a 

 time without mycorhiza. Probably there is some other reason 

 for this, because the Salicaceae (e.g. Poplars), which have typical 

 coral-branched mycorhiza, are almost exclusively multiplied by 

 slips. 



1 Hoveler, ("iib. die Verwerthung d. Humus bei d. Ernahrung d. chloropliyll- 

 fuhrenden Pflan/en." Inaug. Diss. , Berlin, 1892}, states that roots are able to 

 utilize the soil-constituents without aid of fungi. 



- Tubeuf. Forxt. -natunoi**. Zeituchrift, \ 896. 



