ich was quickly followed by other publications by
Kurt Sprengel, L.C. Treviranus (1779-1864), and others. In 1812 J.J.
P. Moldenhawer isolated cells by maceration of tissues in water. The
work of F.J.F. Meyen and H. von Mohl in the middle of the 19th century
placed the study of plant anatomy on a more scientific basis. Reference
must also be made to M.J. Schleiden (1804-1881) and F. Unger
(1800-1870), while in K.W. von Nageli's investigations on molecular
structure and the growth of the cell membrane we recognize the origin of
modern methods of the study of cell-structure included under cytology
(q.v.). The work of Karl Sanio and Th. Hartig advanced knowledge on the
structure and development of tissues, while A. de Bary's _Comparative
Anatomy of the Phanerogams and Ferns_ (1877) supplied an admirable
presentation of the facts so far known. Since then the work has been
carried on by Ph. van Tieghem and his pupils, and others, who have
sought to correlate the large mass of facts and to find some general
underlying principles (see PLANTS: _Anatomy of_).

The subject of fertilization was one which early excited attention. The
idea of the existence of separate sexes in plants was entertained in
early times, long before separate male and female organs had been
demonstrated. The production of dates in Egypt, by bringing two kinds of
flowers into contact, proves that in very remote periods some notions
were entertained on the subject. Female date-palms only were cultivated,
and wild ones were brought from the desert in order to fertilize them.
Herodotus informs us that the Babylonians knew of old that there were
male and female date-trees, and that the female required the concurrence
of the male to become fertile. This fact was also known to the
Egyptians, the Phoenicians and other nations of Asia and Africa. The
Babylonians suspended male clusters from wild dates over the females;
but they seem to have supposed that the fertility thus produced depended
on the presence of small flies among the wild flowers, which, by
entering the female flowers, caused them to set and ripen. The process
was called palmification. Theophrastus, who succeeded Aristotle in his
school in the 114th Olympiad, frequently mentions the sexes of plants,
but he does not appear to have determined the organs of reproduction.
Pliny, who flourished under Vespasian, speaks particularly of a male and
female palm, but his statements were not founded on any real kn