8o PLANT PHYSIOLOGY 



penetrate between the outer root cells, but confine themselves to the inter- 

 cellular spaces. The presence of the fungus is associated with changes in the 

 external form and anatomical structure, which enable the presence of myco- 

 rhiza to be recognized easily, and which must have some physiological signifi- 

 cance. One point is especially noticeable, viz. that roots possessing fungus 

 develop no root-hairs (Fig. 45), and hence the whole absorption of nutrient salts 

 and water can be effected only through the mediation of the fungus. This is 

 the chief difference between the ecto- and endotrophic types of mycorhiza, 

 for in the latter most of the fungus lies in the interior of the cells, and is only 

 connected slightly with living regions outside. While in many plants possessing 

 endotrophic mycorhiza the fungus is essential, this does not appear to be the 

 case in forest trees, for they occur both in the natural condition and also grow 

 perfectly well in cultures without any fungus. NOBBE (1899) succeeded in ob- 

 taining excellent results with pine, spruce, larch, and beech grown in pure quartz 

 sand, free of humus; without any fungus, during a period of twenty-five years. It 

 is possible that in these cases the fungus is nothing more nor less than a parasite, 

 for the fact that the plant does not suffer from the presence of the fungus must 

 not be taken as evidence against parasitism. On the other hand, there is the 

 possibility that the fungus aids the flowering plant in absorbing nutriment, 

 and the three following possibilities may be considered : (i) the fungus might 

 combine nitrogen ; (2) it might absorb salts of ammonia from the humus and 

 work them up so that the flowering plant would thus be a peptone-organism. 

 Since, however, its behaviour in a water culture negatives this possibility, we 

 must turn to the third alternative, viz. that the fungus does not meet the 

 nitrogenous demands of the flowering plant, but that it aids it in taking up 

 materials of the ash (STAHL, 1900). 



I. 38 P. 242, 1. 13, for The part played . . . here also, read Obviously 

 according to this view the function of the higher plant must lie in providing 

 carbohydrate, and of the fungus in supplying minerals already built up (i.e. assi- 

 milated). This conception, how r ever, which STAHL also considers to hold good 

 for endotrophic mycorhiza, presents certain difficulties. 



242, 11. 20-38, for Several problems . . . possesses], read Again, MULLER'S 

 (1902, 1903) studies on the pine have shown very clearly that the mycorhiza is 

 absent in humus soils, but present in sandy soils ; the tree grows, however, 

 much better in humus without a mycorhiza than in sand with it. Many pro- 

 blems still await solution, and it is astonishing how little experiment has taught 

 us in regard to this subject. Still, systematic experiments should not be con- 

 sidered as hopeless, for roots without the fungus are not difficult to obtain and 

 the consequences of infection should make themselves apparent in some way 

 or other. 



244. Lecture XXXI is made XIX in the 2nd German Edition and comes in here. 



247. Lecture XX is incorporated in the 2nd German Edition partly with 

 Lecture XXI and partly with Lecture XXIII. 



251, 1. 3, for (1882, Vorlesungen iiber Pflanzenphysiologie, p. 618) read 

 (Lectures on Plant Physiology, p. 509) 



II. 32-5, delete A detailed description ... of these lectures. 

 1. 37, for Basidiobolus read an alga 



1. 47, for of the original Basidiobolus remains read of an alga remain 



252, 1. 7 P. 253, 1. 13, for Numberless correlations . . . KEENER, 1891, 

 &c.) read In addition to adaptation to function, the plant also shows adaptation 

 to its environment. If we study plants which live together in the same kind of 

 surroundings, we find they have the same general characters, even though they 

 belong to different families, and have no phylogenetic relationship. Closer 



