THE SIMPLER ORGANISMS 



95 



and by the taste of the alcohol in it and by the odor of the 

 escaping carbon dioxide* arising from. it. It may be 

 demonstrated by examination of a drop of the fluid with 

 the microscope. 



Molds and other fungi. — These are chlorophylless plants 

 of different organization. They parallel the filamentous 

 algae in their structure. The common black mold Mucor, is 

 a much branched, vacuolated and multinucleate cell, of a 

 form recalling the green felt (Vaucheria) . Penicillium (figure 

 56) consists of branching filaments recalling in their form 

 those of Cladophora. Molds live for the most part on a 

 more or less solid substratum of organic matter and repro- 

 duce vegetatively by means of spores that are distributed 

 through the air. Therefore, they have differentiated into 

 two parts: the mycelium, the part immersed in the sub- 

 stratum, and concerned with gathering food, a tangle of 



slender root-like fila- 

 ments; and slender 

 aerial sporophores 

 that rise from the my- 

 celium at time of fruit- 

 ing and bear the spores. 

 Many molds feed 

 upon the bodies of plants 

 and animals, living and 

 dead, and upon ma- 

 terials extracted there- 

 from, obtaining both their carbon and their nitrogen 



Fig. 55. Penicillium. a, a little tuft of the 

 mould, as it appears, growing on the sur- 

 face of a nutrient medium ; b, a bit of the 

 same, magnified; s, the original spore; m, 

 mycelial filaments; h, sporophores, with 

 spore clusters; c, one of the spore clusters. 



*A simple chemical test of the presence of CO 2 in the escaping 

 gas may be made by thrusting a glass rod with a drop of lime 

 water suspended on it into the mouth of the culture bottle. The 

 calcium oxide (CaO) of which lime water is a solution, readily 

 unites with free carbon dioxide to form a white precipitate of 

 calcium carbonate CaC03 (CaO-|-C02 = CaC03) which may be seen 

 to form in the drop. 



