PLANT CELLS AND LIVING MATTER. 93 



their discoverer, Max Schultze, were termed " thorns or 

 prickles." It is also known that upon applying a 2 per cent, 

 solution of silver nitrate to fresh epithelia, the cement-sub- 

 stance assumes a dark brown hue, and appears perforated by 

 numerous light transverse lines ; while if, on the contrary, a 

 one half per cent, solution of gold chloride be applied to epithe- 

 lium, the bioplasson reticulum in its interior assumes a dark 

 violet tint, the cement substance remains unstained, and in it 

 Max Schultze's thorns, also coloured deep violet, appear very 

 plainly. Thus it has been proved that the wall of cement- 

 substance does not completely isolate the single epithelia, but 

 is pierced by bridges of living matter which interconnect all 

 epithelia into one continuous bioplasson mass. 



I placed pieces of the flower of " Norimbergia " into a 2 per 

 cent, solution of silver nitrate for about half an hour, then 

 washed the specimens with distilled water and exposed them to 

 daylight. I found that nitrate of silver does not invariably 

 affect the cellulose alone, but sometimes stains also the "cell"- 

 contents ; a corresponding general tinction occasionally hap- 

 pens in the case of animal epithelia. Frequently, while the 

 cellulose wall on the inner surface of the flower Avas compara- 

 tively little coloured by the silver salt and dark granular pre- 

 cipitates filled the spaces between the radiating cellulose off- 

 shoots, the polygonal frames on the outer surface of the flower 

 were beautifully stained dark brown by the silver salt; and 

 examined with ToUe's immersion lens, showed numerous 

 interruptions in their continuity, as represented in fig. 2, 

 exactly like the light-coloured transverse markings seen in 

 cement-substance of animal epithelia under similar circum- 

 stances. Usually the hairs were stained deeply brown; in 

 many compartments one or several light fields were seen, of 

 irregular shapes, freely branching; the periphery of such a 

 light- coloured field often looked serrated, and a reticulum pro- 

 ceeding from it pervaded the whole compartment. This 

 appearance is shown in fig. 3. In a number of instances I 

 observed that the septum separating two neighbouring com- 

 partments was marked by light-coloured lines, as represented in 



