THALLOPHYTA. 



683 



and 388 7 ) and plaited; the whole of the exposed surface of this receptacle is covered 

 with asci. The Morel (Morchella esculenta, fig. 388 l ) possesses a thick stalk bearing 

 a large fleshy receptacle marked out in pitted areas. Nearly allied is the genus 

 Geoglossum, possessing club-shaped receptacles, black in colour, and covered with 

 asci. G. difforme, 2-4 inches high, is often met with among grass in the autumn. 



The Lichenes belonging to this family are treated with the other Lichens 

 at p. 691. 



Reference to a small group of forms, the Saccharomycetes or Yeasts, may be 



Fig. 888. Discomycetes. 



i The Morel (Morchella esculenta). Vertical section of the fertile surface of the Morel showing five asci with their spores 

 and filamentous paraphyses between the asci. Peziza (Helotium) Tuba. * Anthopeziza Winteri. * Peziza vesiculosa. 

 Helvetia infula. ^ Helvetia fistulosa. 1, *,,,' nat. size ; x 4 ; a x 120. 



introduced here. They constitute a detached family with ascomycetous affinities, 

 and characterized by their very peculiar mode of life. For the most part they 

 do not form mycelia, but increase by budding and by the formation of spores. 

 Saccharomyces cerevisece is the well-known Brewer's Yeast. The cells are oval and 

 colourless, and provided with one or more conspicuous vacuoles; the cell-nucleus is 

 not readily demonstrable, though there is little doubt of its existence. Growth 

 here is by budding, little processes being pushed out at the periphery at one or more 

 spots and gradually enlarging (figs. 387 4 - 5 ' 6 ); ultimately they are cut off from the 

 parent-cell by the completion of the membrane across the point of union. In this 



