314 IOWA ACADEMY CF SCIENCE Vor,. XXV, 191?, 



for stratifying, October Id. Planted in ureenliouse, March 14. 

 (Jerniinated, April 14. Leaves narrowly elliptical, margin wavy 

 strongly penninerved ; slig'htly pubescent on upper surface, more 

 pubescent on midrib of under surface. Stipules narrow, acumi- 

 nate, pubescent. As the young leaf unfolds, the margins are 

 involute. Stem reddish, scales small. Seeds of Q. imhricaria, in- 

 out door seed bed, had g-erniinated by June 5, .6 per cent. 



URTICACE^. 



Comparatively few of the woody Urticaceie have bee.i studied 

 Baillon^^ figures the sieed of Celtis australis. The (\ occkJrnialis 

 is described by Lubbock.^*' The' same author describes Madura 

 aurantiaca Aiidi'Morus alba. La ilaout and Decaisne^" figTire the 

 mulberry. Sudworth^^ states of CeJtis occidentaJis that the 

 seeds are rather difficult to germinate, being i;pt to "lie over"' 



for a season before they grow, unless planted or falling in a soil 

 that is constantly moist. The germination of the seeds of the 

 family is variable. Celtis, Morns and others require a period of 

 rest, while elms germinate soon after the seeds are mature. Lub- 

 bock notes that seven different types of cotyledons have been 

 observ'ed ])y him in this family. 



ULMUS L. Elm. 



Vlmus L. Elm. The fruit is a one-celled and one-seeded sa- 

 mara, seed without endosperm and with large cotyledons. The 

 seeds of only three species have been studied; namely the slip- 

 pery elm ( Ulmus fulva iMichx.) and the American elm (T. ameri- 

 cana) and the Chinese elm (T. pumila). 



Ulmvs americana L. American white elm. The seeds were 

 placed in damp cloth and germinated in a few days. The ger- 

 mination is epigseous. 



Ulrmis (imericana L. Hlocmi, ^fiiy 1, seeds falling, May 27. 

 1917. collected IMay :^1. 1917. The radicle iLSually appears first 

 outside the samara. Then the caulicle pushes out, bearing two 

 oval cotyledons and tiny plumule. The cotyledons fall soon after 

 germination. The caulicle is pubescent. The cotyledon>s are 

 glandular })ubescent. Hoot hairs are abumlantly produced upon 



'•'■Natural Ilistory of Plants.. Eii^l. Translation, r,, p. 14 3. 

 '"A contribution to our knowledge of .'^eedlinjrs. 2, p. 493, /. GiG. 

 '"Systems cf Botany. Ensl. Translation, p. 670. 

 '^Forest Trees of llie Pacific Slope, p. 32.3. 



