300 RESEARCHES ON FUNGI 



because of its high efficiency because it prevents jostling and 

 saves time. 



The analogy, which has just been drawn between the basidia 

 on a hymenial area coming to maturity in successive generations 

 and the soldiers in a battalion passing a given point in the line of 

 march, is only a rough one and fails in certain details. Thus, on 

 any hymenial area, there is a wave of development (the details 

 of which have already been discussed) of such a nature that the 

 basidia of the present generation, proceeding from one side of 

 the area to the other, unlike the leading four in a column-of-fours 

 of a battalion, are progressively more and more advanced. Other 

 defects in the analogy we need not- discuss. 



We have seen that on each gill developmental waves pass over 

 the hymenium in an irregular manner : they clash and meet one 

 another in a way which can only be determined by observation ; 

 and to these waves the phenomenon of mottling is due. What 

 advantage, if any, is there in the existence of these waves ? With 

 the wave-system of organisation we find that there are present 

 on the gill a large number of hymenial areas in different stages of 

 development : there are not only black, brown, and white areas, 

 but even the areas of one kind, e.g. the black areas, do not keep 

 developmental time, for some of them shed their spores sooner 

 than others. The general want of synchrony between the areas 

 is advantageous to this extent, that it enables the fruit-body as 

 a whole to shed spores not intermittently, in discontinuous showers, 

 but in a constant stream. Very many plants which produce a 

 large number of organs of dissemination have arrangements w r hich 

 secure that these organs shall be gradually and not simultaneously 

 set free. Thus in many Mycetozoa, Liverworts, and Puff-balls, 

 elaters or capillitium threads are present from which the spore- 

 dust only disentangles itself with difficulty with the passage of 

 time ; and even in the capsules of certain Orchids elater-like hairs 

 play a similar role in the dispersal of the seed-dust. 1 



In this connection one may also cite the capsules of Epilobium, 

 Salix, Populus, etc. These, which contain many small seeds, open 



1 E. Pfitzcr, in Engler und Prantl, Pflanzenfamilien, Teil II, Abteilung 6, 

 Orchidaceae, 1889, p. 73. 



