6o2 Price. — Some Studies on the Structure of the Plant Cell 
in the development of the study of colloids, a study which has made 
enormous progress during the last decade. In the field of biological thought 
this £ Kolloidchemie 5 has had a very great influence, and it is leading to 
a better understanding of many reactions and processes. 
It had become increasingly evident that the substance protoplasm, 
both of animal and vegetable life, was of a colloid nature (Price, 1 . c., ’ 13 ; 
Czapek, ’ 05 , pp. 34 sqq., and references there cited), and so, as was to be 
expected, an investigation of protoplasmic structures by dark-ground 
illumination methods produced some highly interesting results. 
The first examinations of the structure of the plant cell by the method 
were made by Dr. Gaidukov (’ 06 , four refs.) and published in 1906. The 
greater part of the published work in this direction has been performed by 
this investigator, whose results and conclusions will be found in his work, 
‘ Dunkelfeldbeleuchtung und Ultramikroskopie in der Biologie und in der 
Medizin ’ (TO), especially in Sections VI and VII. No detailed account ol 
his work will be given in this place. A short outline of this has been 
published (Price, 1 . c., T 3 ), and constant reference will be made to his results 
throughout this account and in the general discussion. 
It will be enough to state here that he showed how the method could 
be applied to the observation of the Jiving contents of the plant cells, 
especially of filamentous Algae, plant hairs, and such few-celled structures. 
He established, as a main result, the fact that the protoplasm is a hydrosol 
complex (in the terminology of the colloid chemists) in most cases, which 
on the death of the cell is coagulated and converted into the hydrogel 
state (Gaidukov, TO, p. 61 ; see also Bechold, Tl). In most cases the 
hydrosol is seen to consist of a heterogeneous complex — a large number of 
particles of usually submicroscopic size (ultra-microns) rapidly oscillating in 
a fluid homogeneous substratum — the so-called disperse and continuous 
phases respectively. This, as has been shown by Zsigmondy and many 
other investigators, is the general character of a liquid colloid or hydrosol 
‘ solution though the size and number of particles present may vary 
enormously (Zsigmondy, 1 . c., ’ 09 , p. 21 1, Plate I, &c.). In certain cases no 
such rapid movement of the particles was made out, and Gaidukov inclines 
to the view that this was due to the fact that the microns were so small in 
size and so closely packed that no definite particles could be distinguished 
(TO, p. 61). As is well known, such hydrosol solutions do exist; in fact, 
there must be supposed to be a complete range in size of the particles from 
molecular to microscopic dimensions. The coagulation of the hydrosol 
results in the cessation of the motion of the particles, with the production 
of an appearance of large overlapping diffraction images, a frequent character 
of gel structure when observed by dark-ground methods (ib., p. 61). 
The movement of the particles above mentioned is of the nature of 
a Brownian movement — a phenomenon previously well known for small 
