CHAPTER XVII 



CHLOROPHYCEAE. GREEN ALGAE 



For experiments in most phases of botanical microtechnique, no 

 group of plants affords better material than the green algae, since the 

 killing, fixing, and staining can be watched directly; the effect of the 

 change from one solution to another can be observed; and even the be- 

 havior during infiltration with paraffin can be determined with con- 

 siderable accuracy. 



Since the Chlorophyceae furnish our best illustrations of the evolu- 

 tion of the plant body, the origin and development of sex, and also the 

 beginning of alternation of generations, they occupy a prominent 

 place in any well-planned course in the morphology of plants; and, if 

 they were better known, the ease with which the reactions of the indi- 

 vidual cell may be observed would make them valuable to the physi- 

 ologist. 



They are found in both fresh and salt water, but are most abundant 

 in fresh water. The ponds, ditches, and rivers of any locality will yield 

 an abundance and variety both of the unicellular and the multicellular 

 members of this group. Most of the algae are independent, but there 

 are epiphytic, endophytic, and saprophytic species. The larger forms 

 and those which grow in tufts or mats are readily recognized in the 

 field. Many of the smaller forms are attached to other water plants. 

 Drain the water plants and then squeeze them over a bottle. The 

 sediment is Hkely to contain a variety of unicellular and other small 



algae. 



Many of the genera are easily kept in the laboratory. It is not 

 necessary to have very large aquaria. Ordinary glass battery jars 

 holding about a gallon are good for most forms. Jars holding 2 gallons 

 wiU be as good or better. For some cultures which are to be kept for 

 a long time, like Scenedesmus, small glass jars, or dishes, with ground- 

 glass tops are desirable. For a limited amount of material, quart or 

 2-quart fruit cans are very efficient. Put about an inch of pond dirt in 

 some, clean sand in others, and in still others use a gravel bottom. 

 Many forms grow well without any soil or sand in the bottom of the jar. 



When possible, use the water in which the algae were growing, since 



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