THE FOOD OF PLANTS. 95 



and laid on a moist filter paper in a dish which is then covered 

 with a glass plate, a luxuriant growth of fungi will develop on 

 them. Especially interesting is the appearance of the whitish 

 sporophores, about 1 mm. in diameter, of Chondrioderma difforme, 

 a Myxornycete, respecting the culture of which Strasburger l 

 gives exact instructions. In experiments which I made, there also 

 appeared on the stalks after some time the red-tinted sporophores 

 of a Peziza. 



If fresh cow-dung is placed in a dish, and covered with a bell- 

 glass, it becomes clothed in the course of a few days with a luxu- 

 riant fungus vegetation. This is the case both when the dung is 

 exposed to the light and when light is completely excluded. First 

 there appear above the substratum the sporangiophores of Mucor 

 Mucedo, which may attain the length of some centimetres, each 

 sporangiophore bearing at its summit a roundish sporangium. It 

 is instructive to submit this well-known fungus to microscopic 

 examination. Later there comes to view another f ungus belong- 

 ing to the Mucorini, viz. Pilobolus crystallinus. This has short 

 sporangiophores and comparatively large, hemispherical, black 

 sporangia. After a few weeks there is found one of the cap-fungi, 

 with a long stalk and small cap, viz. Coprinus, and finally there 

 often appear the yellowish or brownish cup-shaped sporocarps of 

 Ascobolus. All these fungi develop their mycelium in the dung, 

 while the spore-producing parts project above the substratum. 

 Since the organisms mentioned, like all fungi, contain no chloro- 

 phyll, they maintain themselves at the expense of the organic 

 matter of the dung. 



If we put a fly into water taken from a pond, it quickly decom- 

 poses, and generally representatives of the genus Saprolegnia or 

 Achlya develop on it. Microscopical examination of the white 

 threads surrounding the fly show us that the plant is at first uni- 

 cellular. Later a club-shaped sporangium is jointed off from the 

 end of each branch. 



See Strasburgar, Practical Botany. 



37. Saccharomyces cerevisiae. 



If we tease up some pressed yeast in a drop of water on a slide, 

 and lay on a cover glass, we shall find, on microscopic examination, 

 that, in addition to the small, almost spherical yeast cells, large 



