166 Lake Maxinkuckee, Physical and Biological Survey 

 2. GREATER DUCKWEED 



SPIRODELA POLYRHIZA (Linnaeus) 



Abundant, floating on the surface of quiet waters. In general 

 it thrives best on the surface of calm pools, where the water is per- 

 manent. When found in lakes at all, it harbors in the quiet shallow 

 bays. It is usually associated with interesting forms of animal life 

 such as Hydra, Vorticella, and the like. In the lake it is found near 

 the Inlet, also in permanent ponds. These, as well as some of the 

 other duckweeds, seem to form a favorite food for various insects, 

 as one often finds them badly marred by having portions gnawed 

 out of the margins of the fronds. The stomach of one duck exam- 

 ined contained duckweed in abundance. 



3. IVY-LEAVED DUCKWEED 



LEMNA TRISULCA Linnaeus 



This is one of the most beautiful and curious of the duckweeds 

 with its elongate semi-transparent green fronds with their peculiar 

 manner of branching, a side shoot coming from each side of each 

 frond at the middle, and forming a very regular but intricate and 

 complicated branching system where conditions are favorable, and 

 the fronds tilting at all sorts of angles to avoid interference. Be- 

 sides the minute and inconspicuous Wolfiella floridana, this is our 

 only duckweed which will cling together with other plants of the 

 same species in masses forming coherent tangles. It grows much 

 more vigorously under leaves in shallow water than in unprotected 

 places, and hardly looks like the same plant in different situations 

 although the general form of the fronds is always the same. 

 Found along the lake shore east of Farrar's (September 24, 1900), 

 in a dried-up pond southwest of the lake (October 1, 1900), and 

 by the boathouse near the Inlet (October 2, 1900) . It is abundant 

 at the southeast end of the lake near Norris Inlet during all sea- 

 sons when there is no ice. Found also occasionally along shore 

 among cattails and rushes, as north of Winfield's and at various 

 other places. 



On October 24, 1900, an immense amount of this species was 

 found drifted in Lost Lake, near the middle of the western shore. 

 This formed a thick tangled "scum" extending some way from 

 shore and also making great masses in the bottom. It was also 

 frequently found growing and thriving well in wet places among 

 dead leaves in the water, and appears to hibernate in such places. 



