MITOCHONDRIA 171 



after forty-eight hours' fixation. It may be on this account that 

 the presence of the reticulum had not been observed in plant cells 

 by previous investigators. The Golgi apparatus is more or less 

 definitely localised in position. It is abundant in periblem and 

 dermatogen, and also in the youngest layers of the calyptrogen. 

 Mitosis is active in this region, and the Golgi reticulum persists 

 throughout nuclear division. In the remaining tissue of the root 

 tip, i.e., the central plerome strand, in which the cells are already 

 beginning to elongate and vacuolate, the Golgi network is absent. 

 When secondary rootlet formation is about to occur, the Golgi 

 apparatus disappears from the cells of the primary root tissue, 

 but by the time that the secondary roots are J to 1 cm. long, 

 the Golgi network reappears in the primary dermatogen and 

 periblem. In the meanwhile, the dermatogen and periblem of 

 the root initials become possessed of the Golgi reticulum. In 

 the tertiary rootlets the Golgi network is well marked. In the 

 phase of primary root growth, during which the Golgi apparatus 

 is absent from the meristematic cells, the cytoplasm of these cells, 

 though devoid of a distinctly blackened network, is not homo- 

 geneous. A colourless system of canals ramifies through it, and 

 from its appearance, colourless, in contrast with the blackened 

 network of the secondary roots of the same axis, it may be con- 

 cluded that the development, or at least the maintenance, of a 

 canalicular system is independent of the usual canal contents. 

 In other words, the usual osmic-reducing substances, proteins, 

 lipoids and fats are absent. The accumulation of water from the 

 condensation of amino-acids during protein synthesis is suggested 

 as a possible origin of the Golgi apparatus in plant cells by this 

 author. 



MITOCHONDRIA 



Mitochondria or chondriosomes are small granules, globules, 

 rods, or sometimes thread-like structures, which are always to 

 be found in the cytoplasm. Their presence has led to endless 

 discussion as to their nature and function in the living cell. The 

 most usual view, as far as the higher plants are concerned, is that 

 they are primarily concerned with the formation of the chloro- 



