6 Charles E. Bessey 



(Pine Ridge, and Wild Cat Mountains), and from these to the 

 bluffs of the Niobrara, and North Platte rivers. From the latter 

 it spread to scattered stations along the eastern edge of the Great 

 Sandhill region (Holt, Greeley, Valley, Custer, Lincoln and 

 Franklin counties). 



Bass wood or Linden (Tilia americana L.). The wing is an 

 extension and enlargement of the bract of the peduncle of the 

 inflorescence. The several spherical, dry fruits at maturity are 

 attached nearly at right angles to this wing, which is slightly 

 bent and twisted. At maturity the bract carrying the fruits 

 separates at its base from the tree, and when caught by the wind 

 whirls horizontally, carrying its freight of seed-bearing fruits 

 often to a distance of many metres from the parent tree. The 

 linden occurs abundantly in the forests bordering the Missouri 

 River southeast of Nebraska, and it now extends up that river 

 along the eastern edge of the state (i6) and along the Niobrara 

 River to Cherry Coimty. It has also extended up the valley of 

 the Blue and Republican rivers on the south to Jefferson County, 

 and the Platte River in the central portion of the state, to Nance 

 County. 



The Elm (Ulmns spp.). The flat seed-pods are winged on 

 their margins so that the surface is increased several times. 

 When ripe they are very light, and are easily carried by the wind 

 tq a distance of ten to twenty or more metres from the parent 

 tree. While great numbers fall to the ground under the tree, 

 many are carried to a distance equal to or more than that of the 

 height of the tree. 



The White Ehn ( Ulmns americana L.) is very abundant in 

 the valley of the Missouri River southeast of Nebraska, and 

 thence eastward to the Atlantic Ocean. From the southeastern 

 forest body of this species it has extended up the several river 

 valleys into all portions of the state (17) to the western counties. 



Rock Elm (Ulmns raccmosa Thomas) occurs commonly in the 

 forest belt bordering the Missouri River southeastward, and from 

 this region it has moved upward along the eastern border of the 

 state (18) and up the Niobrara River near the northern bound- 

 ary. While it has been recorded from but two stations (Cass 



16 



