194 The Botanical Gazette. [May, 
given almost entirely to the fully developed tissues and the 
solid cellular framework of plants. In the course of these re- 
searches the methods of investigation were improved, and ob- 
servations were no longer made on crushed or torn objects, 
but on delicate sections. The improvements in microscopes, 
which were made at the same time, greatly aided such studies; 
and when one compares the figures made in successive dec- 
ades, one sees how great have been the advances in the 
graphic reproduction of the objects seen. One may say that 
this sort of investigation of the plant body reached its fullest 
development during the thirties, and that the works of HUGO 
VON MOHL (of Tiibingen, died in 1872) are its crowning 
achievements. By M. J. SCHLEIDEN (1839-1863 in Jena, died 
in 1881) the life history of plants was brought into promi- 
nence and declared to be the necessary foundation of every 
morphological conception. Schleiden’s works were also the 
first in which the attention of investigators was directed to the 
cell-contents. From this time on, morphological study with 
the microscope began to develop in different directions; one 
which, at the same time that notice was taken of the develop- 
ment, was but the continuation of the former phytotomic re- 
searches, anatomy strictly so-called; another, which concerned 
itself with the cell-contents, cell-structure, and the origin of 
the tissues, histology; the third, whose main problem was the 
development of the members of the plant body, the solution of 
which was sought by the study of growing points and of form- 
ing embryos. These three directions were indicated by 
Schleiden and N&GELI (of Freiburg and Munich, died in 1891), 
in part by the latter only. A contemporary of Schleiden, 
Nigeli excelled him in keenness of understanding, in critical 
power, and in observing faculty. 
Nigeli’s researches into the growth of the stems and roots 
of vascular plants, published in the year 1858, laid the founda- 
tions of plant-anatomy. In this work Nageli developed from 
the purely morphological standpoint a classification of tis- 
sues, distinguished various types of growth, and finally traced 
the course and arrangement of the fibro-vascular bundles 1n 
the plant. Phytotomic investigation with morphology as the 
foundation was carried on by H. von Mohl, Schacht, Dippel, 
Frank, Count Solms-Laubach, Sanio, and von Hanstein. © 
these, SANIO (a teacher in Lyck, in East Prussia, died in 
1891) undoubtedly won most credit. His work, without the 
