38 



PRACTICAL BOTANY 



38. Partnership of roots and filaments of fungi. Many of the 

 llowerless plants known by the general name of fungi form 

 a dense network of very minute threads. Such a network is 

 found in intimate association with the roots of many kinds of 

 flowermg plants. It is especially com- 

 mon on the roots of those which cannot 

 manufacture plant food by photosyn- 

 D^-'; ,1 7 j©^ thesis, but it also occurs on other plants 



-^fft^^i^aCUl with green leaves, such as pines and 



beeches. On the roots of the beech 

 the fungus filaments are found united 

 into a sort of membrane, covering the 

 tips of the young roots and extend- 

 ing back for a considerable distance 

 (Fig. 24). In such plants as the heaths, 

 blueberries, and their relatives, the 

 fungus threads form little tangled 

 masses mside the cells near the sur- 

 face of the root and send out free ends 

 into the surrounding: soil. In 



Fig. 24. Tip of a root of 



European beech, covered 



with mycorrhiza 



Thecoating has been strippeil 

 off lor a little way at the 

 top to show the thickness of 

 tlie mycorrhiza. Magnified 

 30 diameters. After Pfeffer 



g ov^xi. j^^x any case 

 the whole filamentous mass living in 

 connection with the root is called a 



mycorrhiza. Roots provided ^^'ith my- 

 corrhiza usually form few or no root hairs, and it is supposed 

 that the fungus threads to some extent perform the work of 

 root hairs in absorbing soil water. The subject is not yet 

 well understood, but it would seem that certain trees, such as 

 pines and oaks, do not flourish as well when grown ui a soil 

 which does not develop a mycorrhiza upon their roots.^ 



1 See " Experiments in Blueberry Culture," Bulletin 103, Bureau of Plant 

 Industry, U.S. Dept. Agr. 



