RATE OF DEVELOPMENT OF INDIVIDUAL SPORES 49 



oreades, which measured 9 '5 X 5' 6 //, took 1 hour and 5 

 minutes. 



So long as a spore has a smooth, rounded wall, the rate of 

 development does not seem to be specially influenced by spore- 

 shape and is not correlated with greater or less rotundity. As we 

 shall see shortly, however, the rate may be affected by the flattening 

 of the cell- wall so as to give the spore a polyhedral form, and by 

 the development of warts. 



Collybia velutipes, Dacryomyces deliquescens, Marasmius oreades, 

 Exidia albida, and Calocera cornea all have very short periods for 

 their development, namely, from 47 minutes to 1 hour and 20 

 minutes. The period for Collybia dryophila was also found to be 

 a little more than one hour, but it was not measured exactly and 

 therefore has not been included in the results given in the Table. 

 All these species are characterised by the fact that they can with- 

 stand desiccation for some days or weeks without any impairment 

 of their vitality : when the dried fruit-bodies are moistened once 

 more, they completely revive and within a very few hours begin to 

 liberate a fresh crop of spores. 1 All these species have spores with 

 smooth, thin, colourless walls. It would appear that their fruit- 

 bodies are so organised that they can make the best use of tem- 

 porary moist weather-conditions by beginning to discharge spores 

 as soon as possible after they have been re-wetted by rain water. 

 Collybia fusipes, which can develop and shed its spores in just 

 over one hour, has been set down in the Table as having fruit- 

 bodies which can withstand desiccation. This, however, is so far 

 only a supposition ; it is not the result of experiment and may 

 not be true. All that has been ascertained at present is that the 

 young fruit-bodies can lose a considerable amount of water without 

 injury and that, like Marasmius oreades, etc., they can reabsorb 

 water when this is brought into contact with their pilei. 



Armillaria mellea and Collybia radicata, species which grow on 

 wood and have smooth, thin-walled, colourless spores, also develop 

 their spores very rapidly in 1 hour and 30 minutes. Possibly 

 this rapid rate of development is associated with the fact that 

 both species grow on wood and are therefore subject to the danger 



1 Vide these Researches, vol. i, 1909, Chap. IX, pp. 105-119. 

 VOL. ii. 



