130 RESEARCHES ON FUNGI 



in response to the resistance offered by mechanical obstacles. One 

 can observe the moulding effect of the pressure exercised by dung- 

 balls and glass by looking at developing rudiments through the 

 glass base of culture dishes. The developing rudiment is also 

 anhehotropic ; but, since at this stage of its existence it is growing 

 in a dark crevice, even if it were positively hehotropic its direction 

 of growth could not as yet be influenced by Hght. The soUd stipe- 

 base, as it continues to grow in length, gradually becomes sensitive 

 to the stimulus of gravity. As a consequence, it makes a geotropio 

 curvature upwards and so brings the axis of the tiny pileus into a 

 vertical position. The stipe-base is thick and very soUd, and the 

 pileus with which it is crowned is very small, pointed, hard, and 

 smooth. The whole of the young fruit-body, for such we may now 

 call it, forms an admirable boring instrument for penetrating through 

 the superincumbent faecal dung-mass. The top of the solid stipe- 

 base, as it elongates, pushes the pileus upwards with so great a 

 pressure that the latter is compelled to force its way between two 

 or three dung-balls or even to break a way upwards through the 

 actual substance of the dung. Since, as we have seen, a young fruit- 

 body is able to lift a mass of nearly half a pound in weight and 

 individual dung-balls only weigh from one to three ounces each, 

 this forcing of a way upwards into the Hght is accompUshed 

 quite easily by the pressure of the growing stipe-base. Until 

 the pileus has been pushed up into the light, its development is 

 delayed : it remains as a small cone capping the upper end of the 

 cyhndrical stipe-base. The significance of this delayed development 

 is obvious : it allows of the pileus being used as an efficient 

 point for the boring instrument, i.e. for the fruit-body as a whole, 

 during the time when the penetration of the dung -mass must be 

 accompUshed. 



As soon as the pileus has emerged above the dung-mass into the 

 light, the hght acts upon the fruit-body in such a way that the 

 further elongation of the soUd stipe-base is inhibited. The length 

 of the stipe-base is therefore decided by the distance through which 

 the young fruit-body has to grow upwards through the dung-mass 

 in order to bring the pileus into the hght. The advantages accruing 

 from the fruit-body having a soUd base to its stipe where the solid 



