There are considerable differences in size and form amongst the spores of the _Agaricini_, although at first globose; when mature they are globose, oval, oblong, elliptic, fusiform, and either smooth or tuberculated, often maintaining in the different genera or subgenera one particular characteristic, or typical form. It is unnecessary here to particularize all the modifications which the form and colour of the spores undergo in different species, as this has already been alluded to. The spores in the _Polyporei_, _Hydnei_, &c., are less variable, of a similar character, as in all the _Hymenomycetes_, except perhaps the _Tremellini_. [Illustration: FIG. 46a.--(_a_) Spore of _Gomphidius viscidus;_ (_b_) spore of _Coprinus micaceus_.] [Illustration: FIG. 47.--Spores of (_a_) _Polyporus cæsius_; (_b_) _Boletus parasiticus_; (_c_) _Hydnum_.] When an Agaric is mature, if the stem is cut off close to the gills, and the pileus inverted, with the gills downwards on a sheet of black paper (one of the pale-spored species is best for this purpose), and left for a few hours, or all night, in that position, the paper will be found imprinted in the morning with a likeness of the under side of the pileus with its radiating gills, the spores having been thrown down upon the paper in such profusion, from the hymenium, and in greater numbers from the opposed surfaces of the gills. This little experiment will be instructive in two or three points. It will illustrate the facility with which the spores are disseminated, the immense number in which they are produced, and the adaptability of the gill structure to the economy of space, and the development of the largest number of basidiospores from a given surface. The tubes or pores in _Polyporei_, the spines in _Hydnei_, are modifications of the same principles, producing a like result.