274 IOWA ACADEMY OF SCIENCE Voi.. XXVIII, 1921 
Tilia were not stratified, but were taken from the trees in March, 
1921.) 
Pinaceae 
Tsuga canadensis (L.) Carr. Hemlock. See figure 36. 
These seeds lay protected on the surface of garden soil from 
October 25, 1920, to March 25, 1921, when they were planted in 
the greenhouse. On April 2, 1921, first leaves made their ap- 
pearance above ground. 
Fig. 36. Tsuga canadensis. Hemlock., Hypocotyl, arched as it emerges. Young 
seedling bearing hull on tips of leaves. Seedling freed from hull. Drawn by C. M. 
King. 
The first part to be seen is the arched hypocotyl; as soon as 
the leaves straighten they bring the hull of the seed with them, 
holding the tips of the leaves together. This hull clings to the 
seedling for some days before it is thrown off. When it is cast 
the cotyledons, three or four in number, emerge. They are of 
equal length (about half an inch), green with steel blue cast, 
slender, uniformly linear, faintly margined. The caulicle soon 
assumes an upright position and the cotyledons spread wide apart. 
The first series of true leaves, three to six in number, soon appear. 
Juglandaceae 
Cary a illinoiensis (Wang.) K. Koch. See figure 37. 
Placed in the garden for stratification October 28, 1920. Lifted 
after a mild winter, March 15, 1921, and transferred to the green- 
house. The shoot appeared above surface April 7, 1921 ; at end 
of two weeks had put out the first three leaves. Germination 
hypogaeous. 
