THE PSEUDORHIZA OF COLLYBIA RADICATA 349 



kinds of elements are disposed parallel to the longitudinal axis of 

 the primordium. A study of successive stages revealed that the 

 so-called root arises from the multiplication and elongation of the 

 two sets of elements just mentioned. Thus, by intercalary growth, 

 that part of the primordium which is to expand into the aerial stipe 

 and pileus is gradually carried upwards to the surface of the soil 

 where alone it attains its full development. Fayod's description 

 of the development of the fruit-bodies of Collyhia radicata, unfortu- 

 nately, was not accompanied by any illustrations. 



Fayod pointed out that the term root is unsatisfactory in 

 describing the subterranean part of the stipe of such a fungus as 

 Collyhia radicata, because the so-called root has neither root-cap 

 nor vascular bundles and arises exclusively by intercalary growth 

 and "not from an apical growing point. The so-called root also 

 differs from a true root in that it grows vertically upwards instead 

 of more or less downwards. In order to indicate that the basal 

 subterranean part of the stipe of Collyhia radicata and other similar 

 Agaricaceae is something different from a true root, Fayod gave 

 to it the name jpseudorhiza.^ 



My own observations on Collyhia radicata, so far as th'fey have 

 gone, confirm those made by Fayod. At Heyshott in England, in 

 September, 1913, there were several fruit-bodies growing around 

 the base of an old Beech tree. On carefully excavating the soil 

 surrounding the pseudorhizae, I ascertained that each of the fruit- 

 bodies was growing just above a Beech root. I succeeded in 

 definitely tracing one of the pseudorhizae downwards through the 

 soil and in making out its attachment to a buried root (Fig. 175, B). 

 The pseudorhizae of the other fruit-bodies were traced downwards 

 through the soil for several inches, but they broke off just before 

 their points of connexion with a root were reached. Owing to the 

 brittleness of the most slender and deepest part of a pseudorhiza 

 and to the compactness of the soil, it is often not easy to free a 

 pseudorhiza from the soil without breaking it or detaching it from 

 the root upon which it has grown. However, in my father's garden 

 at Birmingham, by taking more time and care than was possible 

 at Heyshott, I succeeded in exposing two pseudorhizae 16 cm. long 



1 V. Fayod, loc. cit., pp. 214-215. 



