14 VARIATION AND DIFFERENTIATION IN CERATOPHYLLUM. 



without breaking off many of its branches was practically impossible. 

 We had, then, to be content with few specimens. The individuals in 

 these series were fairly large, and considering the dates of collection 

 may be taken as representative of the "adult" condition of the plant. 

 In other words, it is not probable that if these plants had been left 

 undisturbed much further growth would have taken place that year. 



To sum up: Series I, II, and III, include 8 complete Ceratophyllum 

 plants, coming from quiet water near the shore of Carp Lake in north- 

 ern Michigan. These plants were collected in mid-summer, the three 

 collections covering a period of time of approximately one month, and 

 may be considered to represent the condition at the height of the grow- 

 ing season. 



Series IV. —This series was collected at Ann Arbor, Michigan, on 

 October 15, 1902. The plants were taken from a very extensive and 

 flourishing bed of Ceratophyllum which grew at that time' near shore 

 in the shallow back-water below the dam across the Huron River. 

 The water was comparatively quiet, but there was always a slow- 

 current, which after heavy rains became rapid. So far as this factor 

 in the environment is concerned the Series IV plants represent dis- 

 tinctly different conditions than do those of Series I, II, and III. 

 The character of the bottom was also somewhat different. In the river 

 habitat there was very little of the mass of plant debris which in ponds 

 and lakes accumulates under Ceratophyllum beds. Apparently a con- 

 siderable part of this material was carried away by the current in 

 the river. The plants were attached; that is, the proximal ends were 

 embedded in the soft mud of the bottom. The water at the point where 

 the collection was made was approximately 18 inches deep. The bed 

 was shaded by overhanging trees and bushes on its east side, but was 

 fully exposed on its west side. As will be noted, the collection was 

 made late in the season, so that the plants may be regarded as certainly 

 full grown. 



The series includes two plants. One of these was a very large one, 

 bearing over 900 whorls and over 100 branches. In some respects this 

 was the most satisfactory series of all. There were comparatively few 

 broken whorls and the large size of the individuals gave an excellent 

 collection of data. 



Series V and F/.— The plants in these series all came from a small 

 pond formed as a cut-off of the Huron River. It is situated some Si- 

 miles below Ann Arbor, just west of the upper end of the Geddes mill- 

 pond. The pond still retains its connection with the river through a 



^Later this bed was completely washed away by the breaking of a dam in a spring 

 freshet. 



