BASIDIA AND THE DISCHARGE OF SPORES 19 



that, at present, it seems impossible to subject them to chemical 

 analysis. However, a drop doubtless consists chiefly of water : 

 for it has a perfectly rounded form during its excretion, behaves 

 like a drop of water when touched, on contact with another similar 

 drop unites with its fellow to 

 form a single drop, refracts 

 light like water, is colourless 

 and transparent, and undergoes 

 rapid evaporation in unsatur- 

 ated air. But it would be rash 

 to assert that the drop consists 

 only of water in view of the 

 investigations by Knoll l upon 

 the supposed drops of water 

 excreted from the ends of the 

 pileal hairs of Coprinus ephe- 

 merus, Psathyrella disseminata, 

 etc., various cystidia, and the 

 sporangiophore of Pilobolus. 

 Knoll discovered that all these 

 drops contain a colloidal con- 

 stituent which appears to be 

 mucilage. This he proved by 

 observing the irregular form of 

 the drops when contracting 

 during evaporation, the solu- 

 bility of the drops in water 

 and their insolubility in alcohol, 

 etc. ; and he came to the conclusion that the mucilage is formed 

 by local mucilaginisation of the cell- wall. Knoll also showed that, 

 as the drops dry up, crystals of calcium oxalate are often formed. 

 This occurs for example in the drops on the ends of the cystidia 

 of Inocybe trichospora. In view of these observations it may well 

 be asked : do the drops excreted on the hila of the spores of 

 Hymenomycetes contain mucilage ? By analogy I strongly suspect 



1 F. Knoll, " Untersuchungen liber den Bau und die Function der Cystiden 

 und verwandter Organe." Jahrb. f. wiss. Bot., Bd. L, 1912, pp. 453-501. 



D E F G 



FIG. 9. Lepiota cepaestipes. A-C, ab- 

 normal excretion of water from the 

 hilum of a very rudimentary spore. 

 A, first appearance of a drop at the 

 hilum of the right-hand spore. B, the 

 drop has grown and has enclosed the 

 spore. C, the drop has now attained 

 its maximum size. D-G, normal dis- 

 charge of a ripe spore as seen from 

 above. D, one spore is left on the 

 basidium. E, a drop of water has 

 been excreted at the hilum and has 

 attained its maximum size. F, the 

 spore has been shot upwards and has 

 fallen at G. The drop of water which 

 was carried with the spore has 

 evaporated and is not represented. 

 Magnification, 990. 



