IOWA ACADEMY OF SCIENCES. 
205 
Orchis. 
167. 0. spectabilis L. Moist woods; scarce. 
Habenaria. 
168. H. hracteata (Willd.) R. Br. Dry, open ground; 
infrequent. 
169. H, leucophcea (Nutt.) Gray. Damp meadows; 
frequent . 
Gyrostachys. 
170. G. cernuaih.'jKuntze. iSpiranthes cernua^ith,) 
Wet meadows; scarce. 
juglandacb:^. 
JuGLANS. 
171. J. nigra L. Woods; common. 
172. J. cinerea L. Woods; abundant. 
Hicoria. 
173. H. jninhna (Marsh.) Brit. {Cary a arnara Nutt.) 
Woods; abundant 
174. H. ovata (Mill.) Brit. {Cary a alba JMutt.) High 
woods; common. A hybrid between this and the 
preceding species occurs. 
SALICACE^. 
PoPULUS. 
175. P. alba L. Occasionally spreading along roadsides. 
176. . P. balsamifera candicans (Ait.) Gr. Sparingly 
escaped along roads. 
177. P. grandidentata Michx. Frequent in woods. 
178. P. tremuloides Michx. Common in woods. 
179. P. deltoides Marsh. (P. monilifera Ait.) Common. 
Salix. 
180. S. nigra Marsh. Common in wet ground. 
181. S. amygdaloides Anders. Mostly along streams; 
frequent. 
182. S. alba vitellina (L.) Koch. Rarely escaped. 
183. S . fluviatilis Nutt. {S. longifolia Muhl.) Com- 
mon along streams. 
