410 Prof. H. Karsten on the Formation, 



If, notwithstanding, I now find, after the repeated and most 

 careful examination of this interesting plant, that the law of 

 development laid down by me is followed also in the formation 

 of the cells of its tissue, particular difficulties must indeed have 

 been thrown in the way of the recognition of the true phenomena 

 by the structural conditions of this plant. 



And it is undeniable that such hindrances do exist in the mode 

 of development of the cells of this plant, — dependent, in the first 

 place, upon the existence of a large number of secretion-cells in 

 the vegetation-cells concealing their youngest phases and render- 

 ing observation difficult; secondly, upon the fact that in the 

 tissue-cells the youngest joints do not, as is commonly the case, 

 remain a long time undeveloped and exhibit their characteristic 

 nucleus ; and thirdly, upon the circumstance that the successive 

 endogenous development in this plant proceeds in a high degree 

 even in the secretion-cells, whereby the distinctive characters of 

 the vegetation- and of the secretion -cell become confused and lost. 



It is partly by these circumstances that the recognition of the 

 true developmental processes in this plant has been rendered 

 difficult (as indeed Jessen has shown by the communication of 

 his observations on various Algse), but partly also by the method 

 of investigation, in which chemical reagents have been employed 

 as physical aids. 



In the following account I shall relate my observations in the 

 order dictated to me by the opportunities I had of making them 

 upon the developing plants. 



It has been noticed, in the case of several Algse, that individual 

 cells detach themselves from the cell-tissue of the organism, be- 

 come free like gonidia or the buds of more complex plants, and 

 at length produce perfect individuals. This phenomenon (which 

 takes place in nature under certain, though as yet not fully un- 

 derstood, conditions) may be artificially produced in the Glado- 

 phora glomerata, and probably also in the other Confervse allied 

 to it. 



On cutting a Cladophora glomerata longitudinally into small 

 pieces, so that a cell remains in each portion uninjured between 

 two cut ones, and on placing such sections in water (PI. VI. 

 figs. 30 & 48), a portion df the mucilaginous granular contents 

 is seen to escape from the cut ends of the cells, whilst another 

 portion will become progressively changed and dissolved by the 

 intruding water. The single uncut cell, however, resists the 

 action of the water at its internal transverse septa, now freely 

 exposed, as well as at the cuticle clothing its lateral walls, which 

 does not permit diosmosis to take place in sufficient amount to 

 exert an injurious action upon the assimilative activity of the 

 enclosed cell. The cell thus isolated proceeds in its development, 



