no 



The Plant World 



into the soil to a distance of 15 to 30 cm. A number of these 

 are pictured in outline. 



From a microscopic study of some thirty specimens from 

 a number of widely separated regions in Bohemia, the author 

 concludes that the mykorhiza is in the nature of a gall, or a 

 mycocecidium : the epidermal cells, while still in the dermatogen 

 condition, are stimulated by the entry of haustoria from the 

 hyphae upon the surface. The haustoria draw from the epi- 

 dermal cells a considerable mass of nutrients, which go to the 

 growth of the fungus. The stimulation of the epidermal cell 

 by the fungus is compared to the formation of gall tissues upon 

 leaves, or the development of the endosperm of the eaprifig 

 under the influence of stimulation by the wasp Blastophaga. 



The epidermis remains intact after infection by the fungus, 

 but now shows in each cell a globule of tannin : this serves as an 

 effective barrier against the further entry of the fungus haus- 

 toria, and the cuticularization of certain cell walls confines the 

 intercellular hyphae to regions in which they can do no harm. 



The role of the mykorhiza in the life of the Monotropa is 

 not considered one that is essential to the species: Prof. Peklo 

 believes that the individuals living in soil comparatively free 

 from humus are quite autonomous and independent. He does 

 not attempt to explain how they get their nourishment, and those 

 who have been accustomed to look to chlorophyl and sunshine 

 are left wondering and bewildered. On the other hand, the 

 specimens that occur in humus soil he believes to be entirely 

 dependent upon the fungus for their nutrition. The amount of 

 humus is not generally sufficient to support the Monotropa, 

 but the mycelial network covering the roots serves to modify 

 the soil juices that percolate through it, as through the velamen 

 of orchids: and from this modified liquid the root-surface proper 

 absorbs selectively the materials it can use. 



If the Monotropa can flourish without chlorophyl and with- 

 out mykorhiza, especially in soils that contain little organic 

 material, it is time to revise our notions about the fixation of 

 carbon in phanerogams. We are prepared to look upon the 

 mykorhizal fungus of forest trees and of green orchids as "harm- 

 less parasites," if necessary; but more time is needed to adjust 

 oneself to the idea of the fungus being parasitic upon Monotropa 

 growing in sand. — Benj. C. Gruenberg. 



