THE CELL 19 



appellations have been applied to mitochondria based on their 

 size, shape, where found, supposed function, etc. Mitochondria 

 have been thought to give rise to other plastids within the cell, 

 such as the chloroplasts. They have also been credited with the 

 important function of carrying hereditary traits, but the evidence 

 for this is also far from conclusive. The most convincing hypoth- 

 esis on the function of mitochondria is that which ascribes to 

 them a purely metabolic activity in which they are concerned 

 with digestion, functioning as starch-splitting enzymes {e.g., in 

 seed germination), or they may be, as Lloyd and Scarth believe, 

 reserve supplies of lecithin for the protoplasm. 



The sometimes rod-shaped, sometimes netlike structure called 

 the Golgi apparatus (Fig. 5), discovered by an Italian of this 

 name, bears often a superficial similarity to mitochondria. Its 

 origin and function are not known; indeed, like some other cell 

 parts, its existence as a normal cell inclusion has been doubted 

 ever since its discovery, but anyone who has seen the Golgi 

 apparatus in all its forms, in a variety of cells, such as those 

 exhibited by de Fano, cannot but acknowledge that whatever 

 the Golgi apparatus may be, it stands for a definite structure in 

 the living cell. It appears to be of rather general occurrence in 

 animal cells. While more typical of higher animals, it has been 

 described as occurring in Protozoa (Endamoeba, the Amoeba 

 found in the sublingual spaces of our mouth). Whether or 

 not there is any counterpart of the Golgi apparatus in plant 

 cells has been answered in the affirmative by Drew, who finds 

 structures in plant cells (when certain preparation methods are 

 used) which he believes to be analogous to the Golgi apparatus 

 in animal cells. The extraordinary vacuoles of varied shape 

 which I. W. Bailey has seen in plant cells (Fig. 18) so closely 

 resemble some forms of the Golgi apparatus that there is some 

 possibility of the latter also being vacuoles. 



Other granules and globules occurring within cells are vesicles, 

 fat droplets, yolk globules, pigment granules, starch grains, 

 starch-producing centers (the pyrenoids in plants), crystals, etc. 

 The crystals formed by plant cells may be very striking (Fig. 11). 



There is a most significant cell process which reveals another 

 exceedingly important cell structure. When cells divide they 

 go through, in nearly all cases, a process known as mitosis during 

 which there appear structures called chromosomes. They are 



