DIV. I 



MORPHOLOGY 



27 



from those formed by the usual mode of cell division, in that the free nuclear division 



is followed by the formation of cells, which have no contact with each other, and in 



the formation of which 



the whole of the cyto- _*< 



plasm of the mother cell 



is not used up. This 



process can be seen in 



the development of the 



swarm cells of some 



Algae, in the developing 



embryo of the Gymno- 



sperms, in Ephedra, for 



example, and also in the 



formation of the spores 



of the Ascomycetes. *A 



single nucleus is present 



FIG. 20. Saccharomyces 

 cerevisiae. 1, Cells 

 without buds ; 2 and 

 3, budding cells. ( x 

 540. After STRAS- 



BURGER.) 



; 



FIG. 21. Successive stages of the delimitation of a spore in the 

 ascus of Erysipht, communis. s, Nuclear network ; n, nucleolus. 

 (x 1500. After HARPER.) 



to begin with in each ascus of the Ascomycetes. By successive divisions eight 

 nuclei lying free in the cytoplasm are derived from this. A definite portion 

 of cytoplasm around each of these nuclei becomes limited by a peripheral layer, 

 which then forms a cell wall. Thus eight separate spores arise (cf. Fig. 381). 

 As the researches of Harper ( 23 ) have shown, the formation of the peripheral* layer 

 proceeds from a centrosome-like mass of kinoplasm (Fig. 21 A) which formed a pole 

 of the spindle in the preceding nuclear division. The nucleus is drawn out towards 

 this mass of kinoplasm. From the latter kinoplasmic radiations proceed (kp] 

 which surround the spore as it becomes delimited, and finally fuse to form its 

 peripheral layer (Fig. 21 B, C, Z>). 



III. THE LARGER NON-LIVING INCLUSIONS OF THE 

 PROTOPLASTS ( 24 ) 



In addition to the minute microsomes which are always present 

 in the cytoplasm, larger non-living inclusions make their appearance 

 in the cytoplasm and chromatophores of all cells as they pass from 

 the meristematic to the mature condition. The cell sap, which in 

 larger or smaller vacuoles is hardly ever absent from a cell of the 

 mature tissues of a plant, has already been mentioned. Besides these 

 droplets of a watery solution, fats and oils and also solid bodies 

 in the amorphous or crystalline condition frequently occur in the 

 cell sap or the cytoplasm itself. Many of these included substances 



