LABORATORY STUDIES 25 
grass leaves or other plants. Mount in dilute potash. 
Threads will be found showing the formation of new cells 
(spores) by fission. 
(b) Add a little sugar (preferably glucose) to a little potato 
water (made by grating up a raw potato and heating with 
water to extract the soluble matter and filtering) and break up 
in it part of a yeast cake (‘‘compressed yeast’) setting the 
solution in a warm place. Examine a small drop of the scum 
or sediment after a few hours for cells showing the type of 
fission called budding. - 
(c) By growing yeast for a few days on a moist slab of 
plaster-of-Paris under a bell jar or, less successfully in many 
cases, on the cut surface of a raw potato or carrot some of the 
cells may be found to have produced four cells by internal cell 
division. 
(d) Make a very thin cross-section through a young flower 
bud, or moss capsule. In the stamens of the former or in the 
interior of the latter, if they are at the right stage, will be found 
cells which have divided internally into four parts which sub- 
sequently become spores, each with a thick wall of its own. 
(e) Take a flower bud of Tradescantia just before opening 
and remove a stamen and mount in water of about the room 
temperature. By examining with proper manipulation of the 
light, some cells near the tips of the stamen hairs may be found 
in division and the main features of the mitotic division of the 
nucleus may be dimly seen. 
(f) Examine specially prepared, stained sections of rapidly 
growing root tips, stamens, etc., where cell divisions are taking 
place frequently. Find and study as many stages as possible 
of the mitotic division of the nucleus and cells. These prep- 
arations require especial technique and cannot be made 
successfully by the beginning student. It is desirable that he 
study good preparations. Such can be obtained of various 
supply houses if the teacher has not the time or desire to make 
them. : 
(g) Cell formation by union can be observed in the conjuga- 
tion of pond scums (Spirogyra or Zygnema) or of black molds 
(Mucoraceae, especially Sporodinia, which is frequent on 
decaying toadstools and can be transferred to bread where it 
grows luxuriantly). 
