196 The Botanical Gazette. [May; 
The cell-theory which Schleiden set forth in 1838, soon 
showed itself to be defective, but it is nevertheless of great 
historical importance. It stimulated Th. Schwann to the 
microscopical investigations of the similarity in the structure 
and growth of plants and animals, which he published one 
year later; and it directed the attention of all to the contents 
of the cells. Soon Nigeli published his, for that time, re- 
markable researches into the formation and division of cells. 
H. Mohl also turned his attention to this new direction, ex- 
haustively studied the appearance which the nitrogenous 
portions of the cell-contents display during their constant 
changes of form, found that they present for the most part 
the phenomena of streaming, and gave to them the name of 
protoplasm. In the year 1850, FERDINAND COHN (of Bres- 
lau) emphasized the identity of the contractile substance of 
animal cells with the protoplasm of plants, and this induced 
the zootomist Max Schulze, of Bonn, in 1863, to extend the 
name of protoplasm to the living substance in the whole or- 
ganickingdom. Theminute structure of vegetable protoplasm 
was described by N. PRINGSHEIM (Jena, Berlin?) in a way 
which is valuable to this day, and our insight into its nature 
was thereby greatly advanced. On the other hand no inves- 
tigations into cell-formation and cell-division, as they were 
conducted by Niigeli, Mohl, Pringsheim, Hofmeister, and 
others, could go beyond a certain point, and necessarily 
led in part to fallacious conclusions, so long as they were 
conducted on living, or at least not ‘‘ fixed” objects. E. 
Strasburger was the first to conduct such investigations on 
suitably hardened material. In the first edition of his 
‘* Zellbildung und Zelltheilung” in 1875, this method was 
systematically employed. Combined with the most extended 
investigations, which included the whole vegetable kingdom, 
and parts of the animal kingdom as well, this method led to 
general results which applied to the whole organic realm. 
This publication stimulated manifold researches, especially by 
the animal histologists, which extended, and in various ways 
corrected, the statements of its author, without, however, 
impairing the value of the most important results therein set 
forth. Strasburger himself, in the third edition of the book 
in 1880, was able to trace back free cell-formation to the 
general phenomena of the origin of cells; and in subsequent 
Died in Berlin, October 6, 1894.—G. Fe. 
