THE SPHAEROBOLUS GUN 303 



teeth. The palisade layer no. 5, being amply supplied with water 

 resulting from the deliquescence or gelatinisation of layer no. 6 and 

 part of layer no. 4, becomes highly turgid. 



At or near its extreme base, as is shown in Figs. 147 and 148, 

 the palisade layer is perforated by strands of filamentous hyphae. 

 Doubtless these strands of hyphae serve to conduct food materials 

 from the mycelium through the palisade layer to the gleba when 

 the palisade layer is becoming specialised in structure in preparation 

 for its mechanical activity and the gleba is developing and ripening 

 its spores and gemmae. 



As shown by Fischer in his illustrations reproduced in Fig. 147 

 and as is evident by comparing Miss Walker's photographs repro- 

 duced in Figs. 149 and 150, the uppermost cells of the palisade 

 layer are not radially elongated but are pseudoparenchymatous. 

 These pseudoparenchymatous cells constitute what is mechanically 

 a weak spot in the palisade layer and therefore a spot where splitting 

 can take place when the force which brings about the opening of the 

 fruit-body becomes effective. Thus the Sphaerobolus fruit-body 

 has a kind of stomium comparable with that of the capsule of a 

 Fern sporangium. 



My own investigations on the structure of the fruit-body of 

 Sphaerobolus stellatus support and extend those of Miss Walker. 

 The six layers of the peridium which she described have all been 

 found and are shown on a smaller scale in Fig. 151 and much 

 magnified in Fig. 154. 



Fig. 151 shows a vertical section through a fruit-body about 

 24 hours before the discharge of the gleba. The fruit-body developed 

 from a layer of mycelium (a) which covered a substratum of horse 

 dung in a laboratory culture. The six layers of the peridium of the 

 fruit-body, from without inwards, can be distinguished as follows : 

 no. 1, a thin mycelial layer ; no. 2, a thick gelatinous layer ; no. 3, 

 a fairly thick pseudoparenchymatous layer ; no. 4, a thin fibrous 

 layer made up of interwoven, largely tangential hyphae ; no. 5, the 

 palisade layer, composed of palisade cells below and becoming 

 pseudoparenchymatous and orange-coloured above in the region 

 where the peridium will break open ; and no. 6, a thin layer of 

 orange-coloured pseudoparenchyma surrounding the gleba and with 



