320 



IOWA ACADEMY OF SCIENCE Vol. XXV, I'JIS 



Crataegus Crus-galli L. Hawthorn. Triehomes long; or short, 

 point :d, sligilitly roug-hened, somewhat larger ax uase; straight or 

 slightly curved, colorless. 



Prunus Padus Tj. The seeds of this oniaineutal European 

 shrub germinate readily in the field. Thousands of the young 

 plants come up under the bearing trees. The first plants ap- 

 peared above the ground April 20 to 23, 1917, about the same 

 time that tlie l)oxehler was observed. Germination in 1918, ob- 



Fig-. 86 



Fig. S7 



Fig. 85. — 1, tricliomes of Crataeyns mcllis ; 2, portion of margin of leaf, 

 sliowing glandular tips of serrations; 3, glandular tip, enlarged. Drawn by 

 C. M. King. 



Fig. 86. — Crataegus tnollis. 1, cotyledons; 2, cotyledons and plumule; 

 3, same expanded. Drawn by C. M. King. 



Fig. 87. — Tricliomes from leaf of Crataegus cms-gaUi. Drawn by C. M 

 King. 



served April 10. Germination eplgfeous ; hypoeotyl smooth, witli 

 s'^ig'ht tinge of red; a tap root wlrieh lengthens rapidly; cotyle- 

 dons of medium size petiolate, fleshy, smooth on upper and lower 

 surface, slightly reddish, venation of the lower surface not evi- 

 dent. Stem above the cotyledons reddish, smooth, stipules linear, 

 ■coarsely serrate. First pair of leaves alternate, smooth, shining. 

 glos.sy. penninerA^ed, margins serrate, nodes fairly short, stem 

 })iirj)lish gi'een, smootli ; petioles reddisli purph\, serrations gland- 



