Chapter X — 99 — Duality of the Ghondriome 



One may object to the above theory on the ground that the 

 two categories of elements do not have the same origin, that 

 they develop separately and do not possess the same functions. 

 This seems to imply that they are of different nature and that they 

 correspond to radically different formations. This would bring us 

 back to the first opinion of Mottier (1918). We shall see, indeed, 

 that in cytology one must be suspicious of analogies in shape, since 

 elements as different as young vacuoles and chondrioconts may 

 show in certain phases of cellular development entirely analogous 

 forms. These forms, moreover, are the forms of chromosomes as 

 well. The histochemical point of view must therefore be the decid- 

 ing factor. 



Fig. 67. — Epidermal cells of bulb scale of Allium 

 Cepa, as seen under the ultramicroscope. 1, lipide granules 

 (Gl) . 2, granules, and the faintly luminous contours of 

 chondriosomes (C) and plastids (P). 



We shall see, however, that this objection is not valid here. 

 Even before it was known that the chondriome of embryonic cells 

 of the phanerogams was composed of two types of different ele- 

 ments, CowDRY (1918) made a meticulous comparison between the 

 morphological and histochemical characteristics of the chondrio- 

 somes of pancreatic cells of the guinea-pig and those of the pea 

 root. In the latter, the two categories are blended in the meristem 

 and were not differentiated by the author. CowDRY concluded that 

 the chondriosomes are identical in the two cases, including, of 

 course, those which are transformed into plastids. (Figs. 62, 63). 



Similar comparisons (Fig, 64) were undertaken by Emberger 

 and Mangenot (1920) between the chondriosomes of fern roots 

 (including the amyloplasts) and those of various organs of the frog 

 (kidney and liver). These observations led to the same results. 



