RESEARCHES ON THE MUCORINI. 51 



elucidating and authoritatively deciding all the obscure and 

 critical points in its life-history. 



The cell is constructed by fastening with Canada balsam, 

 upon a glass slide, a glass ring 4-5 ram. in height, cut from a 

 piece of combustion tubing, and afterwards ground flat at its 

 edges. A thin covering-glass, of the same diameter as the 

 outer edge of the glass ring, forms the upper side of the cell, 

 and is kept in its place by three minute drops of oil placed 

 on the edge of the ring. To keep the contained air always 

 moist, a few drops of water are placed at the bottom of the 

 cell. Finally, a small drop of the nutritive fluid is placed on 

 the under surface of the covering glass, and in this drop the 

 spore to be cultivated is sown. 



This drop of fluid can be examined microscopically in every 

 part, provided that too high magnifying powers are not em- 

 ployed although its margin may be studied with high immer- 

 sion objectives. With low powers the whole of the interior 

 of the cell can be explored, and the fructifications which are 

 produced can be followed in the air of the cell. If we are 

 willing to sacrifice the culture, we can remove the covering- 

 glass and examine the growing fungus in any way we please. 



The cell itself must be kept in an atmosphere saturated 

 with moisture, A tin box with a closely-fitting lid, or 

 covered with a glass plate, will answer this purpose. The 

 slide with the attached cells may be placed on a slab of 

 moistened brick, or the bottom may be covered with moist 

 sand or plaster, and the slides may then be allowed to rest on 

 metal supports (PI. Ill, fig. 1). The same box may, in this 

 case, be arranged to hold two series of slides, and a number 

 of such boxes may be placed, one upon the other, in a hot- 

 air bath at a constant temperature, so that a large number of 

 cell-cultures can be carried on simultaneously. 



This method allows the observer to follow with the great- 

 est ease, hour by hour, all the details of the germination of a 

 spore, the character of the mycelium which it developes, and 

 every phase in the development of its fructification — in fact, 

 the whole cycle of the life-history of the plant, however pro- 

 tracted that may be. There are other obvious advantages in 

 this plan of study. Not the least, of course, is the elimina- 

 tion of the possibility of error which must always attach to 

 any culture where the access of extraneous germs during the 

 progress of the investigation has not been prevented. 



Yet, notwithstanding all precautions, it will often happen 

 that extraneous spores are introduced into the drop of fluid 

 either before or during the culture. But, as the whole drop 

 is under observation, these are immediately detected and their 



