GKOWING PLANTS IN THE LABORATORY 5 



tleraaiids careful thought. The laboratory should have enough 

 microscopes so that every student in a section may have his own 

 instrument. If this is not possible, it is better that the course 

 should be planned along such lines that the microscopic work 

 is largely in the nature of demonstrations by the instructor 

 on such microscopes as are available. Two or three students 

 working together at the same microscope create confusion and 

 secure poor results. There are a number of medium-priced instru- 

 ments on the market, with varying merits, from wliich the 

 instructor must choose for himself. A list of the more prominent 

 firms and agents is given in Sec. 218. It is false economy to 

 attempt to save expense on microscopes at the cost of workman- 

 ship and convenience in form. A set of microscopes may readily 

 be kept on the laboratory tables, protected from the dust when 

 not in use by paper cones, and used by successive sections, 

 although this system demands much more watchfulness on the 

 ])art of the instructor than when each student has his own 

 instrument and is held responsible for its care. 



Growing Plants in the Laboratory 



Window sills and unused space should be utilized as far as 

 possible for keeping fresh and growing material alive in the 

 laboratory, not only for the interest that it arouses but also as 

 a practical matter of foresight which at times saves much diffi- 

 culty. Large jars covered with plate glass make excellent aquaria 

 and give little or no trouble. A surprising number of forms 

 will appear in them from time to time, and very interesting 

 cultures frequently become established. A glass growing case 

 (Wardian case) such as is described by Ganon(j, 7, p. 82, is a 

 most useful piece of equipment, and practically indispensable 

 for much physiological work when conservatories or greenhouses 

 are not available. A bay window shut off from the rest of 

 the room by tight glass screens is better still if the heat can 

 be regulated. 



