GENERAL SUMMARY 299 



which clothes the exterior of the dung-ball. The solid shaft of the 

 stipe-base, which may be from 0-5 to 4-0 cm. long, according to the 

 distance upwards through which the stipe-base grows to bring the 

 rudimentary pileus into the light, is held laterally by the before- 

 mentioned mutual pressure of opposing dung-balls, etc. Thus the 

 whole solid stipe-base becomes fixed within the substratum in a most 

 eflfective manner. Its hold upon the dung is doubtless rendered all the 

 more complete by the densely packed hjrphae which grow more or less 

 radially outwards from all over the surface of the stipe-base and also 

 from the lowest part of the stipe-shaft. These hyphae, which give a 

 woolly or peronate appearance to the parts which they clothe, make 

 their way into crevices between particles of the dung and to some extent 

 contribute to the stability of the fruit- body as a whole. With the 

 elucidation of the various factors which play a part in the fixation of a 

 fruit-body, the problem of fixation for Coprinus sterquilinus may be 

 considered to have been solved. 



The upward pressure exerted by a growing fruit-body of Coprinus 

 sterquilinus was measured and found to be nearly half a pound. The 

 greater upward pressure of larger and more solid fruit-bodies of other 

 agarics has been discussed. 



In response to unilateral illumination, the stipe of Coprinus sterquilinus 

 bends out of the vertical toward the light to the extent of only 8°-15°. 

 A greater bending than this would be disadvantageous for the mecha- 

 nical stability of the fruit-body as a whole. It is evident that, in 

 deciding the exact position of the aerial stipe-shaft, the geotropic 

 stimulus has a greater effect than the heliotropic. 



PART II 



Chapter I. — Social organisation exhibited by individuals of one and 

 the same species has attained a high state of perfection in certain 

 animals, e.g. the hive-bee, ants, termites, and man ; but it is imknown 

 in the Phanerogamia, the Pteridophyta, and the Bryophyta. 



In some of the Thallophyta, namely, certain Algae, the Myxobacter- 

 iaceae, the Acrasieae, the Mycetozoa, and certain Fungi, the individuals 

 of one and the same species become associated to form remarkable social 

 communities. 



In the Algae, the individuals of the same species may be associated 

 in a common gelatinous investment as in Aphanocapsa and Coelosphaer- 

 ium, or may build up a common gelatinous stalk as in Dinobryon, 

 Gomphonema, and Licmophora, or may join to form a coenobium as in 

 Hydrodictyon and certain Volvocaceae. The author is inclined to 

 regard a Volvox not as a colony of individuals, but as a highly organised, 

 multicellular, individual plant. 



