(«4) 



the water, where their buoyancy causes them to float until the 

 approach of cold weather when they sink and escape freezing. 

 Upon the approach of warm weather the formation of gases 

 in the chlorophyl-bearing tissues causes them to rise and float 

 about in such manner that many of them may be carried long 

 distances before germination ensues. This appears to be the 

 only method by which dissemination to any distance is secured. 

 The bulbils show a very weak power of resistance to low 

 temperatures and to desiccation. Specimens taken from the 

 soil and placed in a seed envelope in a laboratory at tempera- 

 tures from 15 to 22°C. were shrivelled and incapable of growth 

 a month later. Others laid on a table wholly unprotected 

 were dead in four days. 



Fig. 4. Cross section of portion of bulbil of Lysimachia terrestris. ^.in- 

 tercellular spaces. B, protoxylem. D, glandular ducts. E, procambrium. 

 .F, sheath. 



A temperature of a few degrees below the freezing point 

 was sufficient to kill them, although a large proportion sur- 

 vived the winter when buried to a depth of a few centimeters 

 in the soil. 



The adaptation by which aerial branches are converted into 



