24H THE AMERICAN MONTHLY [Sept., 



on almost any sort of a foundation. On April 18, Tuesday, I 

 set a dry-yeast cake away under a tumbler having first wet the 

 yeast cake. On the following Monday, it was nearly covered 

 with this mould. The plant also grows on pieces of horse-dung 

 if they are kept under glass to insure that they remain moist. 

 Moisture is an indispensible factor in the growth of all fungi. 

 The plant can be recognized by the long gray threads termin- 

 ated with black spherical spots. I found on a piece of paper that 

 had been standing a year with Mucor on it, very pretty growths, 

 from the spots where the spores had fallen on the paper and 

 germinated. The drawing that accompanies this article is from 

 one of these. 



In Mucor, usually, if the specimen is well nourished, the 

 hyphse are not divided into cells. This makes the plant out to be 

 a single and very elongate cell. There are in specimens grow- 

 ing in a soft medium, like bread, a few hypha^ spread out below 

 to form a mycelium. We must remember that the mycelium 

 is the part which gets the food in the allotment of labor to the 

 different parts of these plants This part in our specimen looks 

 like a lot of roots. It was spread out on the paper and from it 

 drew its food so long as the paper remained moist. The aerial 

 hypha? are not branched. They arise as a single unjointed 

 tube running up to their summit on which they bear the spheri- 

 cal spore-case or "sporangium." The sporangium is a covered 

 case; really, it is a single cell in the interior of which the proto- 

 plasm divides up into a multitude of spores. This same result 

 is reached in Penicillium very differently. There the hypba? 

 produce a great many basidia and these then in their turn pro- 

 duce the conidia while here the spores, which are the equiva- 

 lents of conidia, are produced by the division of the protoplasm of 

 the cell, set apart for that work, at once. In Penicillium a great 

 many cells unite to form the aerial hypha; here only one, to 

 form the hypha and another for the sporangium do all this part 

 of the work. 



The sporangium is covered with a delicate cover which as the 

 plant grows older becomes elastic and finally bursts allowing 

 the spores to escape. I believe the spores are thrown out with 

 some violence, for the paper on the sides of the vessel was liter- 

 ally peppered with their growth in every part. The interior of 

 the hypha under the high power shows the presence of proto- 



