54 



AQUATIC MICROSCOPY FOR BEGINNERS. 



Fig. IT. — Whorl of Leaves of 

 Ceratophyllum. 



figure, and when taken from the water they usually do 

 not fall against the stem, but remain stiffly extended. 



The plant is found in still, 

 shallow places, growing in 

 thick masses with the stem 

 often considerably branched. 

 It makes an excellent retreat 

 for certain Rotifers and 

 worms, but the leaves are so 

 heavy and rigid that they are 

 not as easily prepared for 

 microscopical examination as 

 are those of Myriophyllum; 

 they often refuse to lie flat, 

 and thus tilt the cover-glass and allow the water to 

 run away. 



But with neither of these plants will the student try 

 to place an entire whorl of leaves in the cell. It is 

 always best to clip off with scissors a part of a single 

 leaf, and to examine it for whatever may be attached. 

 Work with the microscope is delicate work, and the 

 smaller the object, within certain limits, the better. 

 Many novices make the mistake of trying to examine 

 too large a specimen or too much of a mass at once. 



LEMNA 'POLYRRHIZA (.Fiff. 12) AND LEMNA . MINOR 

 (Fig. 13). DUCKMEAT. y 



These are small plants, very common and often so 

 abundant that the entire surface of large ponds is cov- 

 ered by them as by a green carpet. The water in 

 such cases is so completely covered and concealed 

 that the observer is tempted for a moment to step on it. 

 The two species resemble each other, yet they differ 

 so widely that a glance will distinguish them. 



