Guilliermond - Atkinson 



152 — 



Cytoplasm 



most diverse appearance : dumb-bell-shaped, granules arranged like 

 a string of beads, club-shaped, spindle-shaped, networks of monili- 

 form filaments. They then become transformed into small, spher- 

 ical vacuoles which always stain uniformly, but as they continue to 

 take in water, they soon appear only faintly colored. They some- 

 times contain a few deeply stained precipitates, which show Brown- 

 ian movement and are caused by the precipitation of some of the 

 colloidal contents of the vacuole under the influence of the dye. 

 These vacuoles fuse and finally, in mature cells, form a single large 

 vacuole which occupies the major part of the cell, pushing the 

 nucleus and cytoplasm to the periphery. The cytoplasm is now- 

 reduced to a thin layer around the vacuole which appears faintly 

 colored and shows only a few precipitates. 



Fig. 96. — Anagallis arvensis. Stages in the formation of a glandular 

 hair on the corolla; anthocyanin pigments pi'esent from the first (in vivo). 



The development of the vacuolar system in the root of the 

 wheat may be quite as easily observed and the phenomena take 

 place in the same way. In most of the phanerogams and the 

 pteridophytes\ moreover, an analogous development of the vacu- 

 olar system is recognized. Excellent examples are furnished by 

 the epidermal cells of very young leaves of Iris germanica, by the 

 cells of very young hairs from the sepals of the same plant (Fig. 

 95), by the glandular hairs on the leaflets of the walnut (Fig. 93), 

 by the leaves of Anagallis arvensis and others. In the glandular 

 hairs, the vacuoles, like those in the teeth of the rose leaflets, con- 

 tain from the very beginning an anthocyanin pigment which makes 



' In the apical cell of the pteridophytes, however, there are found only large liquid vacuoles 

 and in the cells of the meristem which are derived from the apical cell there are no small 

 filamentous vacuoles (Emberger). It seems as if the apical cell had already passed through 

 a stage in which the vacuoles were filamentous and semi-fluid, after which these filamentous 

 vacuoles had taken in water and coalesced. 



