Guilliermond - Atkinson 



172 



Cytoplasm 



1 





nels of other varieties of maize as well as in the seeds of other 

 grains (barley, wheat, rye, oats). Aleurone grains stain deeply 

 with mitochondrial techniques which do not at all stain the liquid 

 vacuoles from which they are derived, except in periods preceding 

 solidification when the stains bring about flocculation of the col- 

 loidal solution, and the formation in the vacuoles of precipitates 

 stainable with iron haematoxylin. 



At the time of germination, when the seed again takes up water, 

 the aleurone grains absorb it and become semi-fluid. At this period 

 they often show again a tendency to elongate into filaments capable 

 of anastomosing in a network. 



At the beginning of hydration, the aleurone grains stain deeply 



and homogeneously with vital dyes. Then 

 the filamentous and semi-fluid, reticulate 

 vacuoles derived from them swell as water 

 continues to be taken in and appear as 

 spherical liquid vacuoles which by coales- 

 cence gradually become transformed into 

 large vacuoles in which the vital dyes cause 

 strongly colored precipitates. 



In sections prepared with mitochondrial 

 techniques, the forms which were reticulate 

 and filamentous, at the beginning of ger- 

 mination, show a heavily stained, compact 

 contour which is filamentous, or granular, 

 and which is surrounded by a clear zone. 

 ^^ W I '^^^ spherical liquid vacuoles, which succeed 



•15^ I * I them, still enclose stained corpuscles but 



these corpuscles become less and less abun- 

 dant, as more and more water is taken into 

 the vacuoles and, finally, in the large vacu- 

 oles, no stained contents are found. 



':-\. 



•A 





Fig. 119. — Tulip. Epi- 

 dermal cells of petals of a 

 dark red variety. Frag- 

 mentation of large vacuole, 

 containing anthocyanin, into 

 small, sometimes reticulate, 

 or filamentous, vacuoles 

 caused by plasmolysis in a 

 5% solution of NaCl. 



Reversibility of form in the vacuolar sys- 

 tem. — Pierre Dangeard's investigations, 

 and our own, describing this development 

 show, therefore, that there exists a certain reversibility between 

 the two vacuolar forms. It has previously been shown that vacuoles 

 ordinarily appear under very diflferent aspects according to the age 

 of the cells : 



1. As numerous, minute, semi-fluid vacuoles which have more 

 or less the shape of the chondriosomes. 



2. As a small number of large, spherical, liquid vacuoles, 

 always containing colloidal substances, but in very dilute solutions, 

 i.e., vacuoles corresponding to the classical definition of vacuoles 

 and capable of fusing into a single enormous element. The first of 

 these is found in embryonic cells, the second in mature cells. If 

 the cells are greatly dehydrated, the spherical liquid vacuoles may 

 lose their water, become concentrated, and may again take on a 

 semi-fluid consistency and look like chondriosomes. A more com- 



