230 MR. S. LE M. MOORE’S STUDIES 
Crüger*, more than thirty years ago, considered that nutritive 
materials might be conveyed by the streaming plasma, and such 
conveyance was actually observed by Strasburgert in the course 
of his study of cell-division in Spirogyra. Meanwhile Velten f 
had put forward the notion that protoplasmie movement is of 
universal occurrence in the vegetable cell. It was left for H. 
de Vries $ to apply Velten’s view to the altered ideas of cell-life 
introduced by the continuity doctrine, by maintaining that the 
transport of materials is brought about by cireulatory or rotatory 
actions in the connected protoplasts. De Vries takes his stand 
upon Stefan's| calculations, according to one of which, for 
instance, one milligramme of sodium chloride in 10-per-cent. 
solution requires 319 days to traverse, by means of diffusion in 
water, the space of a metre; his own experiments with vertical 
tubes, in the bottom of which he placed some coloured salt in a 
dry state and then cautiously filled the tube with water, indicated 
a rate of diffusion wholly inadequate to account for the rapid 
transport of materials through the tissues of plants. He also 
made a large number of observations which showed the univer- 
sality of protoplasmic movement. In these experiments portions 
of tissue were laid in a 5-per-cent. solution of cane-sugar, in which 
they were allowed to remain from one to two hours before ex- 
amination. Under these circumstances either circulation or rota- 
tion was usually set up, and was especially well pronounced in 
the conducting-cells of the phloem, 7.e. where the transport of 
materials is at its maximum. It may be objected to De Vries's 
vertical-tube experiments that they do not reproduce natural 
conditions with anything like exactitude; still, even allowing 
for this, there does seem to be much force in his argument, 
although one is not bound to admit that the normal movements of 
protoplasm are as energetic as were those observed by him, in 
which latter I am inclined to think there are three factors con- 
cerned, viz.: lst, a slow motion, similar to but perhaps slightly 
more rapid than that by which photolysis is effected ; 2nd, in- 
* Bot. Zeitung, 1855. Criiger did more; he even suggested that transport 
of nutriment from cell to cell might take place vid pores in the cell-wall; in 
fact, his theory is in all essentials the same as De Vries's. 
t ‘Ueber Zellbildung und Zelltheilung’; also ‘Bau und Wachsthum.’ 
1 Bot. Zeitung, 1872. 
Bot. Zeitung, 1885 ; most of the bibliography is given in this memoir. 
Sitzungsb. der k. Wiener Akad. 1879, ii. Abtheilung. 
