ERGASTIC SUBSTANCES 



103 



Jeffrey's (1922) view that the druse is formed as a casing around the 

 protoplast being opposed by Lloyd (1923), who contends that druses, 

 more than one of which may be present in one cell, arise within the 

 protoplasm and may later pass into the vacuole. Gaiser (1923) finds 

 that the stellate crystal of Anthurium arises in the vacuole, and that 

 after it comes to occupy nearly the whole cell the cytoplasm with the 

 nucleus can still be seen surrounding it. 



The curious "cystoliths" in the Ficus leaf (Fig. 53, A) represent 

 outgrowths of the cellulose wall heavily impregnated with calcium 

 carbonate. In the cystoliths of certain Acanthacese the calcium may 

 later disappear (Linsbauer, 1921). Crystals of silica are very abundant 



Fig. 53. — Crystalline and other ergastie materials in plant cells. A, cystolith in 

 subepidermal cell of Ficus leaf. B, crystals in Arctostaphylos. C, druse in Rheum pal- 

 matum. D-K, aleurone grains: D, E, from Myristica; F, from Datura: G, from Ricinus; 

 H, from Amygdalus; I, from BerthoUetia; J , from Faeniculum; K, from Elceis. L, raphides 

 from Agave leaf. AI, inulin crystals in preserved cells of artichoke. (B-K after Tschirch.) 



in the thickened walls of wood cells and in many other tissues, such 

 as the outer portion of the Equisetum stem. In an earlier section refer- 

 ence was made to the protein crystals of aleurone grains and to those 

 frequently observed in the nucleus. Mirande (1923) states that the 

 radiocrystals in the epidermis of white-lily-bulb scales consist of a 

 phytosterol which he calls " liliosterine." The carbohydrate inulin, which 

 often occurs in solution in the vacuole, appears as nodules of radiat- 

 ing crystals in tissues which have been preserved in alcohol (Fig. 53, M). 



Recapitulation: Structure of the Protoplast. — In the preceding 

 chapters the various structural elements of the protoplast have been 

 passed in review. Before proceeding further it will be well to draw 

 up a classification of these elements — a classification which in some 

 points must be regarded as provisional only. From the point of view 

 of convenience and present probabilities the differentiations and inclu- 

 sions of protoplasts may be listed as follows: 



A. The Nucleus, a highly specialized organ consisting of 



1. Nuclear membrane, lying against the cytoplasm; 



2. Reticulum, composed chiefly of chromonemata of chro- 



mosomes; 



