THE SPORE AND ITS DISSEMINATION. 



131 



In the Perisporiacei the periihecinm has no proper orifice, or 

 ostiolum, for the discharge of the mature sporidia, ■which are 

 usually small, and are disseminated by the irregular rupture of 

 the somewhat fragile conceptacles. The asci are usually more 

 or less saccate, and the sporidia approximate to a globose form. 

 The asci are often very diffluent. In Perisporium vulgare the 

 ovate brown sporidia are at first, and for some time, attached 

 together in fours in a concatenate or beaded manner. In some 

 species of Erysiphei the conceptacle en- 

 closes but a single sporangium, in others 

 several, which are attached together at the 

 base. In some species the sporangia contain 

 two, in others four, in others eight, and in 

 others numerous sporidia. In Chcetomium 

 the asci are cylindrical, and in most cases 

 the coloured sporidia are lemon-shaped. 

 When the conceptacles are fully matured, 

 it is commonly the case that the asci are 

 absorbed and the sporidia are free in the 

 interior of the conceptacles. 



Of the fleshy Discomycetes the genus 

 Peziza may be taken as the type. If the 

 structure which prevails in this genus be 

 brought to mind, it will be remembered 

 that the hymenium lines an expanded cup, 

 and that the asci are packed together, side 

 by side, with their apices outwards, and 

 their bases attached to a substratum of cells 

 which form the inner layer of the recep- 

 tacle. The sporidia are usually eight in 

 each ascus, either arranged in single or 

 double rows, or irregularly grouped to- 

 gether. The asci are produced in succes- „„ . . 



= r Flo, 66.— Asci, sporidia, 



sion ; the later, pressing themselves upwards and paraphyues of As:o- 

 between those previously developed, cause bolus ( Boudier >- 

 the rupture of the mature asci at the apex and the ejection of 

 the sporidia with considerable force. When a large Peziza is 



