352 
L. H. MACDANIELS 
Nyssa sylvatica Marsh. 
Mature, twig. 
Ostrya virginiana (Mill.) K. Koch. 
Mature. 
Platanus occidentalis L. 
Mature stem, mature root, growing, 
4- yr, stem, 4-yr. root, 2-yr. stem, 
2- yr. root, twig. 
Populus deltoides Marsh. 
Mature, mature root, growing, 4-yr. 
stem, 4-yr. root, 3-yr. stem, 3-yr. 
root, I-yr. stem, i-yr. root. 
Prunus Persica (L.) Stokes. 
Mature. 
Prunus serotina Ehrh. 
Mature. 
Pyrus communis L. 
Mature. 
Pyrus Malus L. 
Mature old tree, mature young tree, 
growing, mature root, 5-yr. stem, 
5- yr. root, twig. 
Quercus alba L. 
Mature, mature root, growing. 
Quercus bicolor Willd. 
Twig. 
Quercus rubra L. 
3- yr. stem, 3-yr. root. 
Rhamnus alnifolia L'Her. 
Twig. 
Rhus typhina L. 
Mature, growing, mature root, 3-yr. 
stem, 3-yr. root, i-yr. stem, i-yr. 
root, twig. 
Ribes americana Mill. 
2-yr. twig. 
Robinia Pseudo- Acacia L. 
Mature, growing, mature root, 4-yr. 
stem, 4-yr. root, 2-yr. stem, 2-yr. 
root, I-yr. stem, i-yr. root, twig. 
Salix alba var. vitellina (L.) Koch. 
Mature. 
Salix nigra Marsh. 
Mature, growing, mature root, 2-yr. 
stem, 2-yr. root. 
Sambucus canadensis L. 
Mature, growing, mature root, 3-yr, 
root. 
Sambucus racemosa L. 
I-yr. stem, i-yr. root, twig. 
Sassafras variifolium (Salisb.) Kuntze. 
Root of small tree, 2-yr. twig. 
Tilia americana L. 
Mature, 3-yr. stem, 3-yr. root, 2-yr. 
stem, 2-yr. root, i-yr. root, twig. 
Ulmus americana L. 
Mature stem, mature root, grow- 
ing, 5- to 6-yr. stem, 5- to 6-yr. 
root, 3-yr. stem, 3-yr. root. 
Ulmus fulva Michx. 
Mature. 
Viburnum Lentago L. 
Mature, growing, mature root, 6- to 
lo-yr. root. 
Methods 
A saw and a chisel were used in obtaining material from the trees. 
This was cut into approximately one-centimeter cubes including 
phloem and contiguous cambium and xylem, and killed in chrom- 
acetic acid, 0.75 percent-i percent. It was then desilicified by placing 
it in hydrofluoric acid, one half commercial strength, for two weeks; 
dehydrated through a series of alcohols; embedded in celloidin; sec- 
tioned on a sliding microtome; stained in Delafield's haematoxylin and 
safranin, and mounted in balsam. It was found that collections made 
in the early fall soon after cambial growth stopped were usually in 
better shape than those made in the early spring before development 
began, because in many species the sieve tubes were badly crushed at 
the latter time. 
The description of material is taken up in phylogenetic order. 
For the sake of brevity, many of the descriptions are omitted and the 
descriptions themselves are abridged. For convenience, the following 
outline is followed for the description of each species. 
