58 SUMMARY OF CURRENT RESEARCHES RELATING TO 
Structure of the Resting Nucleus.* — Dr. F. Krasser has investi- 
gated the structure of the resting cell-nucleus in a number of flowering 
plants (Monocotyledons and Dicotyledons), and in Pteris serrulata and 
Spirogyra, both in the living state and with the use of various fixing and 
staining reagents. He finds it to be always composed of granular 
elements ; in the cases observed the granules were always distinct, and 
usually arranged in short stellate rows. They were most easily detected 
in the interior, with greater difficulty in the membrane of the nucleus 
and in the nucleole ; in the two latter cases there was not always a 
distinct differentiation of granules. The nuclear sap is present only in 
those resting nuclei which, like some of those of Pliajus , have a wide- 
meshed staining framework. The granules belonging to the nuclear 
sap are revealed by staining with cyanin. Some of the granules 
appear to be identical with Pfitzner’s chromatin-granules. With double- 
staining the granules, as a rule, take up only one of the two stains, so 
that they may be distinguished as erythrophilous and cyanophilous. In 
two cases staining showed the nuclear membrane to be composed of two 
lamellas. 
Physode, an Organ of the Cell.| — Under the term physode, Herr 
E. Crato describes a structure which he finds especially in the cells of 
Chsetopteris plumosa , an alga belonging to the Pheeosporese. The 
physodes are vesicular bodies occurring within the protoplasm-filaments, 
which they distend more or less ; they consist of a protoplasmic envelope 
and of strongly refractive fluid contents. In the cells towards the apex 
of a shoot the protoplasm is differentiated into a parietal utricle, and 
into flakes and threads, the latter of which permeate the cell somewhat 
uniformly, forming a network of hexagonal meshes. The threads of this 
mesh are from 0*33 to 0 * 5 /x thick ; and these meshes are again per- 
meated by other finer or coarser threads ; these may be not more than 
0-1 /x thick. Chromatophores and physodes occur in both kinds of 
thread, the former being found especially in the neighbourhood of the 
cell- wall, the physodes more towards the interior, and chiefly near the 
nucleus, which is often concealed by physodes and chromatophores. The 
physodes are usually of a round or elliptical form, and vary in size from 
that of the chromatophores to almost invisible refractive particles. 
They never leave the protoplasm-filaments, and have been hitherto 
included under the microsomes, of which they form the largest portion. 
The physodes are endowed with a characteristic amoeboid movement, 
which is sometimes of a pulsating nature. They are constantly shifting 
their position within the filaments, sometimes returning again to the 
same place, sometimes moving even into another mesh. This is due to 
a power of motion of their own, and not simply to the streaming of the 
protoplasm. They are not unfrequently branched, the branches being 
still always enclosed within very fine threads of protoplasm. 
The physodes do not multiply by division, but are formed fresh 
within the protoplasm-threads by the separation of drops of a strongly 
refractive substance. In the formation of the zoospores of Chsetopteris 
their contents are mostly used up, and fresh ones are formed as the 
* SB. K. Akad. Wiss. Wien, ci. (1892) pp. 560-83. 
t Ber. Deutsch. Bot. Gesell., x. (1892) pp. 295-302 (1 pi.). 
