British Gastromycetes , 7 
enumerated the spores spring from the apex of the basidia, 
but in the genus Tulostoma the club-shaped or semi-cylindrical 
basidia bear four spores placed at some distance from each 
other on the lateral wall (Fig. 33, a). Contrary to what would 
have been expected, the largest, most highly ornamented and 
deepest coloured spores are met with in the least differentiated 
orders, the Hymenogastreae and the Sclerodermeae, and as 
we pass upwards through the Lycoperdeae to the Phalloideae 
the spores become smaller, and in the last-named order are 
always very minute, smooth, and colourless or nearly so, the 
green tinge being mostly due to the dense mass of olive-green 
mucus in which they are imbedded in all known species. To 
the above general statement there are, as would be expected, 
some exceptions ; in Podaxon , a genus belonging to the Lyco- 
perdeae, the spores are large and brightly coloured, but smooth ; 
in some species of Cyathus again the spores are large, but 
smooth and colourless. All spores are colourless during the 
immature state, the colouring matter appearing just before 
maturity. The wall of a ripe spore consists in all cases of at 
least two distinct layers, the endosporium and the exosporium : 
the first always remains smooth, the ornamentation of the 
surface being due to local shrinkage or contraction of the 
exosporium, the uncontracted portions assuming the form of 
spines, warts, sinuous lines, or form a more or less regular 
polygonal network of ridges (Figs. 14 and 70, a). If such 
ornamented spores are treated for some time with a dilute 
solution of potassic hydrate, the contracted portions expand, 
and the exosporium eventually appears as a thick, even, 
colourless membrane surrounding the endosporium. The 
presence of a nucleus can be in many cases demonstrated in 
young spores. The £ nuclei 5 of systematists consist of oil 
globules or vacuoles. 
As already stated, two leading features stand out prominent 
in the evolution of the Hymenomycetes ; the conversion of the 
primitive even hymenial surface into gills, thereby increasing 
the spore-bearing area, and secondly, the gradual concealment 
of the hymenium until the spores are mature. 
