Chapter VII 



61 — 



The Chondriome 





^r\ 



^ o 



^ „ o o 



o O - o 



_ o 



Qa 



numerous, densely clustered, chondrioconts. Then the cell under- 

 goes a nuclear fusion and when that is completed, the two chondrio- 

 somal masses fuse around the single nucleus. After nuclear fusion, 

 the ascus enlarges and grows longer progressively to form an 

 elongated voluminous cell. During this process, the nucleus main- 

 tains a somewhat central position while the chondrioconts, which 

 have been grouped about the nucleus, spread out through the entire 

 cytoplasm which in this phase is filled with small vacuoles. At the 

 same time, at one or several points on their long axis, the chondrio- 

 conts usually form small swellings, each occupied by a vesicle (Fig. 

 28). 



When the growth of the ascus is complete, but a little before 

 the first mitosis occurs, these vesicles disappear and the chon- 

 drioconts, all oriented in the direction of the longitudinal axis of 

 the cell, manifest a tendency to elongate. At this stage a cytoplasm 

 (sporoplasm), dense and rich in chondrioconts, differentiates in 

 the central region of the ascus while 

 the basal and apical portions des- 

 tined to make up the epiplasm, re- 

 main filled with small vacuoles. The 

 nucleus which occupies the center of 

 the sporoplasm then undergoes three 

 successive mitoses during which, it 

 is seen, the chondrioconts remain 

 scattered in the sporoplasm except 

 in the region occupied by the asters 

 where they are completely absent. 

 The divisions completed, each of the 

 resulting eight nuclei remains con- 

 nected with its aster by a small pro- 

 tuberance at the end of which the 

 centrosome still persists. It is not 

 long before the astral fibres them- 

 selves recurve so that, in section, each nucleus then appears as if 

 surmounted by a parasol on whose surface there will first form the 

 limiting membrane of the future ascospore. Now the whole region 

 of the future spore occupied by the centrosome and aster shows no 

 chondriosome at all. All these elements are found exclusively at 

 the opposite pole, where they form a compact mass of entangled 

 chondrioconts. The ascospores then enlarge and become surrounded 

 by a cellulose wall. Not until then do the centrosome and aster 

 disappear. At the same time the nucleus becomes centrally placed 

 in the ascospore and the chondriosomes are distributed throughout 

 the cytoplasm. Only a few chondriosomes remain in the epiplasm. 



In the ascus of one of the Hemiascomycetes, Ascoidea rubescens, 

 Varitchak has described in more recent work, a vesiculation of 

 chondriosomes analogous to that recorded for the higher Asco- 

 mycetes. 



It has also been possible to follow the life history of the chon- 

 driosomes during the development of some of the Agaricaceae, in 



a 



Fig. 26. — Fragments of protoplasm 

 of Achlya. A, at Ihe extremity of a 

 growing filament; B, an older filament. 

 c, chondriosomes. Gl, lipide granules 

 blackened by osmic acid. n, nucleus. 

 Meves' method, stained with acid fuchsin. 



