162 Rudolf Beer. 
Magnus) in the trabeculae of C aider pa, the embryo-sac of various 
Scrophulariaceae and Plantaginaceae, the massulae of Azolla, the 
epidermal cells of the seed coat of several plants, in the suspensor 
cell of Phaseolns and in the cells of the roots of several plants 
which form mycorrhiza. As Tischler points out we cannot cor 
rectly speak of a direct “transformation” of protoplasm, which 
consists largely of proteids, into the carbohydrate material of a 
cell-wall. No doubt the carbohydrate is split off from the proteid 
molecule whilst soluble nitrogenous substances remain over. In 
accordance with Pringsheim’s theory it was long taught that the 
cell-plate, which is formed during cell-division, is directly converted 
into the primary cell-wall separating the daughter cells. This view 
has now been shown to be erroneous by the work of Treub, 
Strasburger and Timberlake. 
The cell-plate splits to form the plasma membranes of the 
daughter-cells and the new cell-wall is secreted between them. The 
double nature of the cell-wall thus secreted by the two new plasma 
membranes is strongly supported by the observations of Allen on 
the middle lamella. There is accumulating evidence to show that 
each new wall and each fresh lamella which is added to a wall is 
only formed in the most intimate connection with the protoplast 
(Klebs, Strasburger). That not only the cytoplasm, but also the 
nucleus is concerned in this work is clearly showrn by the work of 
Haberlandt, Klebs, Townsend, Derschau and Gerassimoff. 
What relative share is taken by the nucleus and by the cyto¬ 
plasm in the organisation of a new wall and in the manufacture of 
the material necessary for its formation cannot yet be decisively 
stated. In nearly all cases which have been observed the nucleus 
can be clearly seen to play a prominent part in both processes, 
whilst in one case at least I have observed that the constructive 
material for the growth of the cell-wall is manufactured at the 
expense of the trophoplasm, whilst kinoplasm and a somewhat 
shrunken nucleus remain at the conclusion of the process. 
In his most recent contribution to cell-wall literature (1898) 
Strasburger has shown that growth in surface of a membrane takes 
place either by passive stretching, accompanied simultaneously by the 
deposition of new lamellae on the face of the stretched membranes, 
or by intussusception (Substanz einlagerung). Growth in thickness 
generally takes place by the deposition of new lamellae upon those 
already present. These lamellae do not usually grow in thickness 
by intussusception (Substanz einlagerung), but in certain cases 
