14 STUDIES OF AMERICAN FUNGI. 



SO that the pileus is again brought more or less in a horizontal 

 position. 



In collecting these plants they are often placed on their side in 

 the collecting basket, or on a table when in the study. In a few 

 hours the younger, long stemmed ones have turned upward again. 

 The plant shown in Fig. 14 {Amanita phalloides) was placed on its 

 side in a basket for about an hour. At the end of the hour it had not 

 turned. It was then stood upright in a glass, and in the course of a 

 few hours had turned nearly at right angles. The stimulus it 

 received while lying in a horizontal position for only an hour was 

 sufficient to produce the change in direction of growth even after the 

 upright position had been restored. This is often the case. Some of 



Figure 14. Amanita phalloides. Plant turned to one side by directive force of 

 gravity, after having been placed in a horizontal position. (Natural size.) 



the more sensitive of the slender species are disturbed if they lie for 

 only ten or fifteen minutes on the side. It is necessary, therefore, 

 when collecting, if one wishes to keep the plants in the natural posi- 

 tion for photographing, to support them in an upright position when 

 they are being carried home from the woods. 



The cause of this turning of the stem from the horizontal position, 

 so that the pileus will be brought parallel with the surface of the 

 earth, is the stimulus from the force of gravity, which has been well 

 demonstrated in the case of the higher plants. That is, the force 

 which causes the stems of the higher plants to grow upward also 

 regulates the position of the cap of the pileated fungi. The reason 

 for this is to be seen in the perfection with which the spores are shed 

 from the surfaces of the gills by falling downward and out from the 

 crevices between. The same is true with the shelving fungi on trees, 



