IIO THE AMERICAN NATURALIST. 
proved this condition to be typical for all herbaceous and shrubby 
species examined, but to be absent in roots of arborescent species. 
She described the alternation of a flattened, usually pigmented, layer 
of cells with one to three layers of rounded cells in each annual ring, 
the flattened layer being the last produced each season. Protoplasm, 
nuclei, and starch grains exist in cork zones four to five rings removed 
outside the phellogen. 
Mıss CAROLINE THOMPSON: The Structure and Development of 
Internal Phioem in Gelsemium sempervirens Ait. The phloem originates 
as four longitudinal tracts in the primary meristem and steadily 
increases, until by the eighth or tenth year it has entirely pressed 
together and destroyed the pith. During the first year nourishment 
of the pith ceases, owing to the differentiation of two layers of cells, 
which were referred to as the “phloem sheath.” 
A remarkable distribution of the internal phloem was shown to exist 
in the petiole, at the base of which a bicollateral bundle arrangement 
exists, but this quickly changes to the ordinary collateral relation by 
the passage of the upper (internal) phloem through the xylem of the 
petiole. Each bundle in passing out into the petiole subdivides into 
three parts, two of which remain in the stem and soon reunite, while 
the third passes out and behaves as above described. 
From the second year onward, the internal phloem patches of the 
stem show areas of crushed and obliterated tissue where the previously 
formed phloem has been pushed inwards by the younger elements. 
In older stems eight large phloem patches, formed by division of the 
original four, entirely fill up the pith area. 
