74 RESEARCHES ON FUNGI 



which have not as yet produced either sterigmata or spores. I was 

 not able to distinguish the third-generation basidia from those of 

 the fourth generation, but simply assume that their numbers and 

 arrangement are like those of the basidia of the first and second 

 generations. A study of Fig. 36, B, will show that irregularities 

 creep into the pattern here and there, and that there is no such 

 mathematical exactitude displayed as in the diagram. This, how- 

 ever, is what one might expect in a living organism, and does not 

 weaken the general conclusion that the elements of the hymenium 

 tend to arrange themselves locally in a symmetrical manner. It 

 was stated that, in ordinary areas of the hymenium where there 

 is no such regular arrangement of the elements as has just been 

 described, the basidia which are beginning to develop spores are 

 as far away as possible from the basidia which already bear spores. 

 The same tendency can be seen where we have the regular pattern, 

 as will appear from a study of the diagram A in Fig. 36. Let us 

 note the position of the basidia of the first generation, a. The 

 basidia of the second generation, 6, arise in the middle of the squares 

 formed by these first-generation basidia and not in the other possible 

 locations, i.e. they arise in the positions which are the most remote 

 from the basidia of the previous generation. 



An attempt was made, by means of the method ^ described in 

 Volume II, to determine the length of time occupied in the develop- 

 ment of the spores of individual basidia. A gill was dissected from 

 a newly gathered fruit-body and laid flat in a compressor cell. A 

 drop of water was then added and the cell closed by its cover. 

 The hymenium was observed in face view with the low power 

 of the microscope. Unfortunately, the basidia continued to grow 

 normally for only a short time, and then the spores on each collapsed 

 together. Several trials with varying amounts of water in the cell 

 convinced me that the isolated gills are very sensitive to changes 

 in the amount of water or water-vapour with which they are in 

 contact, and do not long continue normal development in a small 

 compressor cell. For a single gill a large piece of pileus, including 

 several gills, was substituted. This piece of pileus was inverted 

 from its normal position so that the gills looked upwards. Develop- 



^ Those Researches, vol. ii, 1922. pp. 43—48. 



