CHONDRIOSOMES 



91 



)6 



functions. Others contended that the proplastids should not be included 

 under the heading of chondriosomes nor homologized with anything in 

 animal cells. Meyer's (1920) claim that plastids constitute a funda- 

 mentally distinct class even in their earliest stages of development has 

 been supported by Bowen (1927a6, 1929a), who has employed a variety 

 of methods little used by botanists. In root meristems and other plant 

 tissues Bowen claims that the two classes of elements can be distinguished 

 on the basis of general form, structure, reactions to stains, and behavior 

 during nuclear division and cell-division. As a rule the chondriosomes^^ 

 in the root tips are round and vesicular, are 

 best preserved and stained by the Champy- 

 KuU method, and show no regular arrange- 

 ment in the cell during mitosis; whereas the 

 proplastids are elongate and usually not 

 vesicular, are best preserved by the Mottier- 

 Benda method, and show a characteristic 

 polarized arrangement during mitosis (Figs. 

 25, 47). Bowen further finds, with others,^- 

 that the two classes react somewhat 

 ently in impregnation procedures and 

 reports^^ of unlike reactions to vital dyes \f, 

 and heat. A difference in appearance and ^'^•♦,.6 



behavior in tissue affected with mosaic dis- "<w 



eases is described by Dufrenoy (1931). As p^^ 47.-Piastids and chon- 



a result of his studies on living cells, Pensa driosomes. a, plastids (large) and 



concludes that plastids may arise either by t^fnt'^S 'oTt„t,r t 

 division or by a direct differentiation of the chondriosomes in root tip of Vida; 

 cytoplasm; in the latter case the chondrio- :r:h»dSZ ("darf t"S 



somes group about the plastids and seem to during mitosis in Hyadnthus root. 



furnish material for the latter as they grow ^'^^''' ^'^^"" ^^^^"^"^ 

 or become green. Loui (1930), who has used the fluorescence microscope, 

 can find but one kind of initial body which he regards as chondriosomal 

 in nature. 



It is plain that the confusion in this subject is in part a matter of 

 terminology, since the words " chondriosome " and "mitochondrion" 

 have been used in such different ways. Hence it has been suggested that 

 the terms should be dropped altogether (Mottier, Dangeard). Zirkle 

 (1929c), on the other hand, uses the term "mitochondria" for all small 

 inclusions which are preserved by bichromates with a pH higher than 



differ- »?V^J^ 



d cites %•?. ■ 5;^?:>.\ 





^^ Not wishing to commit himself on the question of the relation of these bodies 

 to the chondriosomes of animals, Bowen employs for them the term "pseudochon- 

 driosomes." Dangeard calls them "cytosomes." 



32 Pensa (1925), Ruhland and Wetzel (1924). 



«« Guilliermond (1923a), Policard and Mangenot (1922). 



