The mode in which the organs immediately containing the seeds are formed, differs according to the family. In the tribe of puff-balls, where the seed is formed in the interior of the fungus, there is no hymenium; a few of the internal cells (when the Lycoperdon has attained its full size) begin to enlarge, and these in a short time are found to contain small granules, generally of a determinate number, and moistened by a fluid secreted from within the walls. In such funguses as have an hymenium it is only some of the superficial cells, and these in a particular position in reference to the receptacle, that contain seeds; though perfect identity of structure throughout, is evinced in a conclusive manner if we invert the head of a young fungus on its stalk; for then these thecæ begin to form and to fill themselves with seed, not on the side where they were about to do so previous to this inversion of the head, but on that which was the uppermost and sterile surface, and which, now that it is the undermost, has become prolific. The expansion of a fungus, according to Vittadini, is effected as follows:—“These thecæ,” of which we have been speaking, “as they swell, become distended with the contained seed, and mostly so at their free extremity, since they have more room for expansion in that direction than at the other, which is impacted into the substance of the pileus; in consequence of this, a series of wedges are formed which, as the seed continues to distend them, force out the pileus, loosen its marginal connections with the stalk, uncurl its involuted borders, and finally open up its cells, pores, and sinuses.”[109]