452 PEOCEEDINGS OF THE ACADEMY OF [July, 



of Plant Morphology and Phj^siology, 1899, the author enumer- 

 ated the substances which could be used to bring out the spherite 

 structure in the starch-grain. The same kind of reagents, but in 

 stronger solutions, may be used to bring out the spherite structure 

 in the wall of thickened parenchyma cells, as endosperm, or 

 lignified cells, as stone cells. In eases where the cell-wall has been 

 metamorphosed into mucilage, simple treatment with water, as has 

 also been shown with the starch-grain, is sufficient to bring out 

 the structure.* The reason that this structure is not apparent 

 under natural conditions is because the refractive properties of the 

 crystalloidal substance so nearly resembles that of the associated 

 colloid. The use of certain reagents, however, which are more or 

 less penetrating in their action, cause an imbibition of water by 

 the colloidal portions with consequent swelling of the grain, or cell- 

 wall, and a contrast in refractive power with the more insoluble 

 and hence unaffected crystalloidal substances. 



Sphere-crystals are further distinguished from spherites in that 

 the latter are capable of taking up or holding certain coloring 

 principles, as safranin, gentian violet, etc. It is questionable, 

 however, if the crystalloids contained in the spherite take up the 

 coloring matters, it being probable that the colloid associated with 

 the crystalloid is the portion that is colored, as I -have already 

 shown in my studies on the structure of the starch-grain. 



In the cell-wall the crystalloids occur in very close radial and 

 tangential rows and constitute by far the greater proportion of the 

 wall. In the starch-grain, on the other hand, there is apparently 

 a greater preponderance of colloidal matter which takes up certain 

 stains. This layering, which is well marked in the starch-grain, 

 is scarcely distinguishable in the cell-wall. The reason that it is 

 not so well marked in the cell-wall is because of the difference in 

 amount of the crystalloidal and colloidal substances, the close 

 arrangement of the crystalloids and also the difficulty of obtaining 

 uniform microscopical sections, as can be readily obtained with the 

 starch-grain, 



(12) Potassium nitrate solutiou (saturated). 



(13) Taunin solution. 



(14) Potassium phosphate solution (saturated). 



(15) Hydrochloric acid (5 per cent.). 



(16) Water between the temperatures of 50- C. and 70^ C. 



^ This wouUl tend to show that the crystalline structure is not due to the 

 precipitation of substances by the reagents used. 



