THE SIMPLER ORGANISMS 



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 s p o r o phore s 

 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. 56. 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 CaCO 3 (CaO + CO 2 = CaCO 3 ) which may be seen 

 to form in the drop. 



