The Structure and Development of Internal 
Phloem in Gelsemium Sempervirens, Ait. 
(WITH PLATE IX.) 
By Carouine B. Tuompson, B. S. 
HE following is the result of observations made during 
the winter of 1897-98, in the Botanical Laboratories of 
the Biological Department of the University of Penn- 
sylvania. The material used consisted of specimens of varying 
age, preserved in alcohol, which had been collected by Pro- 
fessor Macfarlane, while on a trip to Wilmington, N. C., and 
of seedlings grown in the greenhouses of the department 
from seeds collected by him. An abstract of the observations 
upon the stem was read at the meeting of the “Society for 
Plant Morphology and Physiology,” held at Ithaca, N. Y., 
in December, 1897. 
GENERAL LITERATURE. 
In the early years of the present century much confusion 
existed in regard to the terms for the softer elements of a vascu- 
lar bundle. These were variously called bast fibres, bast cells, 
latticed cells, sieve fibres, etc. Hartig, in 1837, was the first to 
correctly describe such elements as sieve tubes, and to regard 
them as the essential constituents of the phloem. Several years 
later, Hartig’s observations were confirmed by von Mohl, 
Nageli and Hanstein. The investigation of plants with internal 
phloem, or phloem on the inner margin of the wood, was be- 
gun by Hartig in 1854, and continued by others. The orders 
Cucurbitacez, Asclepiadaceee and Apocynacee were among 
the first to be studied. In 1875 de Bary originated the term 
“bicollateral bundle,’ a name that has been objected to by 
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