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INTRODUCTION TO CYTOLOGY 



threads, but also in a great variety of irregular shapes (Fig. 43). At 

 present it is customary with the majority of workers to refer to all types 

 as chondrio somes or mitochondria. For those which are definitely rod- 

 and thread-shaped the terms chondriokonts and chondriomites are also 

 used. It is not to be thought that the various forms constitute distinct 

 classes, for several investigators (N. H. Cowdry; M. and W. Lewis 1915) 

 have observed the chondriosomes undergoing marked changes in shape 

 in living cells, granular ones becoming rod-shaped and filamentous, and 

 vice versa. Schaxel (1911) and Kingery (1917) state, moreover, that in 

 fixed material the shape of the chondriosomes is to a certain extent 

 dependent upon the character of the microtechnical methods employed. 







3 



h 



V 



Ffc 43. — Chondriosomes in plant and animal cells. 



A, nerve cell from guinea pig. X 480. (After E. V. Cowdry, 1914.) B, tapetal cell 

 of Nymphoea alba. (After Meres, 1904.) C, living epidermal cell of tulip petal. D, ascus 

 of Pustularia vesiculosa. E, hypha of Rhizopus nigricans. F, portion of embryo sac of 

 Lilium; chondriosomes clustered about nucleus. G, cell of root tip of Allium — (C-F. 

 After Guilliermond, 1918.) 



Although when first discovered chondriosomes were believed to be 

 rather limited in distribution, they have now been reported in the cells of 

 plants and animals belonging to nearly all of the larger natural groups. 

 It is asserted by N. H. Cowdry (1917) that "in all forms of animals, 

 from amoeba to man, which have been investigated with adequate 

 methods of technique, they occur without exception." They are present, 

 furthermore, in the cells of all tissues. In plants it is probable that they 

 are no less universally present, although it has not yet been possible to 

 demonstrate them with certainty in bacteria, Cyanophycese, and certain 

 Chlorophycese, such as the Conjugate and Confer vales (Guilliermond 

 1915). They are abundant in myxomycetes (N. H. Cowdry 1918), 

 Charales (Mirande 1919), brown and red algae, fungi, and all the higher 

 groups. 



A critical comparison of the chondriosomes of plants with those of 

 animals has been made by N. H. Cowdry (1917), who concludes, contrary 



