D IRE CTIONS FOR L A B RA TORY STL'D Y. 3/1 



2. Observe form and particularly the abundant branching. 

 Can a single main axis be traced ? How many branches arise at 

 one point? (Fig. 29.) 



3. Demonstration. Kill and fix the protoplasm of some fila- 

 ments of Cliidophin-a by placing them in chrom-acetic acid 

 (water, 990 parts; chromic acid, 7 parts; acetic acid, 3 parts) for 

 i hour; wash out the acid by placing them in running water 

 for several hours (6-24) or in a large dish of water changed 

 several times in the course of 24 hours; stain by placing them in 

 alcoholic borax-carmine or haematoxylin for several hours. 

 Mount in water. Examine with high power of microscope. 

 Each segment of the filament will be seen to contain several 

 nuclei (more deeply stained than the body protoplasm and the 

 numerous chloroplasts), showing the segments to be ccenocytes and 

 not true cells. (^[ 28.) 



F. STONEWORT (Chara sp.). 



Place the plant in a glass dish with clean water. Set it over a 

 black background if preserved (and therefore colorless) material 

 is used. If fresh, a white dish furnishes a good background. 



1. From the base of the axis carefully remove the mud by 

 washing. Observe the colorless rhizoids. (^[ 37.) 



2. In the body of the plant observe (a) the central axis; (l>) the 

 whorls of lateral dwarf branches ("leaves") at intervals 

 ("nodes"); (c) the single lateral axes arising among the 

 whorled dwarf branches. (If 33, fig. 35.) 



3. Trace the main axis to its tip. Compare the distance be- 

 tween whorls toward the tip. How do they stand close to tip? 

 Dissect away the outer ones successively. What is within? 



4. Demonstration. Prepare or obtain a longitudinal section of 

 the apex of the axis, and show under compound microscope the 

 apical cell and the differentiation and growth of its successive 

 segments. (H 39, fig. 38.) 



5. Compare the length of the various lateral axes. Compare 

 the tip of any of the long lateral axes with that of the main axis. 

 What do the observations show as to the duration of growth of 

 these ? 



6. Compare the length of old and young dwarf branches. 

 Compare their tips with those of either lateral or main axes. 

 What do these observations show as to the duration of growth 

 of the dwarf branches? Observe the form and distribution of 

 the branchlets. Can they continue to grow in length ? 



