29 ELEMENTS OF BOTANY. 
free. It may be found flourishing in unfrozen springs, even in mid- 
winter. 
271. Examination with the Magnifying Glass.1— Float a little of 
the material in a white plate, using just water enough to cover the 
bottom of the latter. Study with the magnifying glass and note the 
green color of the threads and their great length as compared with their 
thickness. Are all the filaments about equal to each other in diameter ? 
Handle a mass of the material and describe how it feels between the 
fingers. 
272. Examination with the Microscope.— Mount 
in water under a large cover-glass and examine first 
with a power of about 100 diameters, then with a 
power of 200 diameters or more. Note the struc- 
ture of the filaments, each made up of a row of cells 
placed end to end. 
| 
Px ft, 
hin ee 
ZZ 
Lio 
i. 
Post 
mats k Move the slide so as to trace the whole length 
4% On of several filaments, and, if the unbroken end of 
e657 one can be found, study and sketch it. 
“eid! Study with the higher power a single cell of one 
r Pup of the larger filaments and make out the details of 
structure shown in Fig. 192. Try to ascertain, by 
focusing, the exact shape of the cell. Count the 
Fic.192.—Cellfroma bands of chlorophyll. The number of bands is an 
Thread of Pondscum jmportant character in distinguishing one species 
(Spirogyra). (Magni- from another. 
fied about 90 diame- : : 
ters.) Run in five-per-cent salt solution at one edge of 
iE. micleus - ch, spiral the cover-glass (withdrawing water from the other 
band containing edge with a bit of, blotting-paper). If any change 
chlorophyll; p, in the appearance of the cell becomes evident, make 
pyrenoids, little » sketch to show it. What has happened to the cell- 
masses of proteid 1 
material with Contents? Explain, by reference to what you know 
starch-grains. of osmose, the cause of the change. 
On a freshly mounted slide run in iodine solu- 
tion, a little at a time, and note its action on the nucleus. Is any starch 
shown to be present? If so, just how is it distributed through the cell ? 
273. Reproduction of Spirogyra. — The reproductive process in 
Spirogyra is of two kinds, the simplest being a process of fission, not 
unlike that with which the student has become familiar in Protococcus. 
The nucleus undergoes a very complicated series of transformations, 
1 Consult Huxley’s Biology and Spalding’s Introduction to Botany. 
