416 VEGETABLE PHYSIOLOGY 



In some of the Thallopliytes the new wall is formed 

 without the intervention of a spindle. After the two new 

 nuclei have taken up their positions, the new wall arises mid- 

 way between them as a ring-like outgrowth from the original 

 cell membrane, and gradually grows inwards till it is complete. 



In the divisions of the protoplasts which constitute a 

 coenocyte the nuclear divisions are not followed by the 

 construction of any cell-walls, so that the limits of each 

 protoplast are not well denned ; in some cases indeed they 

 are indistinguishable. 



The reproduction of the protoplast is sometimes attended 

 by the production of not two but several, which appear 

 simultaneously. Such a case is illustrated by the forma- 

 tion of the endosperm in the embryo sac of the Phanero- 

 gams. It is, however, only a modification of the process 

 already described. The division of the original nucleus is 

 followed by the disappearance of the spindle ; the daughter 

 nuclei divide in turn, and the process is continued until a 

 large number of free nuclei lie embedded in the protoplasm 

 of the cell. These then become connected with each other 

 by the simultaneous development of connecting fibrils or 

 small spindles like the first, and cell plates, which later 

 become cell membranes, arise across them as in the case 

 described. The protoplasts so formed exhibit no differen- 

 tiation among themselves, but are all alike in appearance, 

 structure, and fate. 



This modification of the process of reproduction of the 

 protoplast is known as free cell formation, and in many 

 cases it is attended by a specialisation of function, which 

 will be alluded to a little later. 



In many cases of the reproduction of such plants as 

 consist of enormous numbers of protoplasts variously 

 arranged and differentiated, we have to recognise essentially 

 no other process than the multiplication of the protoplasts 

 by such means as we have just described. Generally in 

 these cases some part of the parent plant becomes detached 

 Tind grows at once into the new individual. We have seen 



