48 M assee : The Evolution of the Basidiomycetes. 
destined to possess their own morphological and physiological 
features, which eventually became fully evolved in the plants 
we now know as fungi, as opposed to the characteristics 
possessed by the algae, from which they originated. In fact, 
so highly differentiated and diverse in structure and physio- 
logical functions are the most modern group of fungi, the 
Basidiomycetes, including the gill-bearing species, or toad- 
stools, that if those alone had survived it would have been 
impossible to have traced any line of descent from the alga;. 
The evolutionary power, whatever that may be, was 
manifest in the pioneers of the fungal world. To cope with 
the difficulty of being confined to an aquatic habitat, many 
of the Phycomycetes produced a second mode of spore pro- 
duction, and in this case the spores were purely asexual in 
origin, and were so constructed that they could be dispersed 
far and wide by aerial agents — wind, animals, insects, etc. 
This step enabled fungi, once for all, to take possession of 
dry land, and from that moment gradual evolution and 
differentiation has progressed by leaps and bounds. The 
second kind of spore production alluded to must be looked 
upon as something new and supplementary to the original 
sexual mode of spore formation previously possessed by the 
fungus, and was the starting-point of a sharply-defined 
division of labour not met with elsewhere so sharply marked 
in the vegetable kingdom. The later asexual spore formation 
is spoken of technically as the conidial stage. This is rep- 
resented by the well-known mildew of the rose. The white 
powder is a mass of asexually-produced spores, which are 
produced in immense numbers, and in rapid succession, so 
long as the plant on which the fungus is parasitic continues 
active growth for the season. These spores are dispersed by 
wind, etc., and those that happen to alight on another rose- 
leaf or young shoot set up a new centre of disease from which 
spores are liberated in turn, and thus the fungus extends its 
area of distribution. That is the function of the conidial 
form of fruit of every fungus, extending its geographical area. 
But there is a period of the year throughout the world, for 
climatic reasons, unfavourable to the growth of fungi. As 
the spores of the conidial condition retain their vitality for 
only a limited period — often for only a few days, they could 
not tide the fungus over that period when it could not continue 
its active growth. The spores produced by the older sexual 
form are not capable of germinating at once, but only after 
a period of rest, consequently they remain in a passive or 
resting condition during that period of the year when the 
fungus could not continue its growth, but when favourable 
conditions return these spores germinate and infect the plant, 
etc., on which the fungus grows, when the conidial condi tion 
Naturalist, 
