Feb., 1905.] Hibernacula of Ohio Wafer Plants.. 291 



For the species of Mononyx, tables will be found in Montan- 

 don's paper; the Mexican and Central American forms of Pel- 

 ogonus are tabulated in Vol. II, Rhvnchota of Biologia Centrali 

 Americana, btit there is no work on Gelastorcoris outside of the 

 notes under the sp3cies in the last mentioned work to help in 

 separating them. 



New York Citv. 



THE HIBERNACULA OF OHIO WATER PLANTS. 



Harlan H. York. 



Many aquatic plants that root at the bottom of streams and 

 lakes die down in the autumn and pass the winter by means of 

 tubers, bulbs and rhizomes, while others have developed a 

 peculiar type of winter propagative buds at the tips of the stems. 

 These curious buds are found in many of the pond weeds, stone- 

 worts and bladderworts. In the late summer and early autumn 

 the plants turn brown and die except at the tips of the stems 

 which remain alive. The tips of the stems cease to lengthen 

 out and are enclosed with dark green leaves which become 

 crowded and folded so closely as to form egg-shaped bodies. 

 They remain on the stems for some time but finally become 

 detached and sink to the bottom of the water where they escape 

 the cold of winter and are scattered in various directions thus 

 becoming a means for vegetative propagation. These buds are 

 much shortened stems and are termed Hibernacula. 



A somewhat careful study was made of the hibernacula of 

 Utricularia vulgaris since they are quite large and easily obtained. 

 They begin to appear in the latter part of August and are formed 

 in the manner already described, the leaves being crowded so 

 closely and overlapping each other as to form green ball-shaped 

 buds that are quite compact. The air spaces in the stems and 

 leaves become much reduced and the cells are packed with starch 

 granules which cause the buds to sink when they are detached 

 from the stems. When the hibernacula first begin to develop, 

 the tips of the stems and leaves secrete a mucilaginous substance, 

 which surrounds and permeates the buds when they are formed. 



In the spring when the ice has melted and the sun's rays 

 begin to warm the water, the buds commence to grow. The 

 starch grains that were stored up in the preceding autumn are 

 used in the building of the new stem. Bubbles of gas are set free 

 which are held in the mucilaginous covering and cause the buds 

 to rise to the surface of the water. The hibernacula have 

 changed somewhat in appearance from that in the fall as they 



