CHAPTER II. THE FORMATION OF CELLS. 



149 



cells, the nuclear division appears to bear no causal relation to 

 cell-division in the same plant. 



A second mode of cell division is that of gemmation, or bud- 

 ding. In this, a minute protuberance is first formed on the 

 surface of the cell ; it gradually increases in size until as large, 

 or nearly as large, as the parent cell, when ordinarily it separates 

 from the latter and becomes an independent organism. Some- 



Fig. 393. 



Fig. 395. 



Fig. 396. 



Fig. 393. — Budding Yeast cell. Magnified about 2,500 diameters. 



Fig. 394.— Small portion of sporocarp of Cup Fungus, showing asci containing asco- 

 pore*. Magnified about 350 diameters. 



Fig. 305. —Mother cell from the anther of Tropeolum, showing the formation of pollen 

 grains by internal cell-formation. Magnified about 600 diameters. 



Fig. 396. — a. Young plant of Oedogonium, reproducing itself by rejuvenescence: b, 

 the escaped protoplasm, after it has acquired cilia and the power of locomotion. Magnified 

 about 350 diameters. 



times, however, they remain attached to each other for a time, 

 forming small chains, but ultimately become independent. This 

 mode is observed only among the Yeast plant and its relations. 

 See Fig. 393. 



A third mode is by internal cell-formation. In this case the 

 protoplasm within the parent cell wall breaks up into two or 

 more rounded masses, each of which eventually acquires a cell- 

 wall of its own, and escapes from the parent cell by the rupture 



