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Botany. — “An investigation on polarity and organ-formation with 
Caulerpa prolifera.’ By Prof. J. M. Janse. (Communicated by 
Prof. Hugo pr Vriss). 
(Communicated in the meeting of October 29, 1904). 
Polarity is a property of very many of the lowest organisms as 
well as of a great part of the cells in the body of the higher plants 
and animals. 
The regular exterior shape and internal structure of organs must 
be partly attributed to the agency of polar influences during their 
development, while the definite vital phenomena of organs must 
also, among other causes, be ascribed to polar actions of the con- 
stituent cells. 
The cause of this polarity, i.e. the property of acting or reacting 
in a certain direction otherwise than in the opposite direction, is 
unknown, and the great difficulty of finding suitable material for 
investigation is perhaps the principal cause of this. 
Former observations made with Cuulerpa prolifera had convinced 
me *) that this unicellular, relatively gigantic and morphologically 
highly differentiated alga must be suitable for this purpose. 
Having had the opportunity during last summer, of submitting this 
plant to a renewed investigation at the Zoological Station at Naples, 
I wish to relate briefly the principal results obtained. 
For a description of the structure of Caulerpa prolifera, as well 
as of its protoplast and the very intense currents that take place 
in it, I refer to my quoted paper. 
For the new experiments the “leaves” were exclusively used, namely 
the outgrowths of the “rhizome” measuring in extreme as much as 22 
centimetres in length and 20 millimetres or a little more in breadth. 
Their little thickness allows us to examine them also microscopically 
in a living condition, while their considerable length and breadth 
make them particularly fit for experiments. Moreover cut leaves or 
parts of leaves can form new rhizomes and rootlets and so can 
regenerate to complete plants by neo-formation. 
Formerly already L used these leaves for experiments concerning the 
course of the protoplasm-currents, in which it was often required to 
make large incisions in the leaves. 
These plants, to be true, often sustain serious lesions which heal 
1) Die Bewegungen des Protoplasma von Caulerpa prolifera, Pringsheim’s 
Jahrb. f. wiss. Bot. 1889, Bd. XXI, pag. 163—284, with 3 plates. 
