Harshberger : Water-storing tubers 275 



cally all of its weight and shrivels up to a small mass of dried 

 material, only one twenty-fifth the size of the original tuber. The 

 observations of Goebel * are apropos. Goebel states that he found 

 Neplirolepis tuberosa (perhaps N. cordifolid) as an epiphytic or 

 terrestrial fern on the road to the Tankoban Prahoe volcano in 

 Preanger, Java. He states that the tubers of this fern, the size of 

 pigeon-eggs, are for the purpose of storing water, for he found that 

 the water content was 96.3 per cent, of the total weight. He 

 further proved this statement by placing tuber-bearing ferns in dry 

 soil. The fronds remained green, although the water supply was 

 extremely small. Gradually, however, the water disappeared from 

 the tubers until they assumed a shrunken form. When grown in 

 wet soil, the tubers retained their normal plumpness. The con- 

 clusion reached by Goebel, therefore, was that these tubers are of 

 importance to the fern in tiding over shorter or longer periods of 

 drought. 



Tubers of Asparagus Sprengeri 



This much-cultivated species of asparagus produces a consider- 

 able number of tuberous roots. The large secondary roots are 

 about the thickness of a telegraph wire and on the lateral roots 

 that grow from the larger ones occur the watery tubers f which 

 range from twenty-five to forty-four millimeters in length and from 

 eighteen millimeters in the larger tubers to ten millimeters in the 

 smaller ones. They are light brown in color and almost perfectly 

 smooth. From their distal extremity, the root is continued and 

 this root continuation may branch and rebranch into numerous 

 subsidiary branches. 



Sections of these tubers mounted in water show large paren- 

 chyma-cells without solid contents, except in a few, small, scattered 

 cells where bundles of raphides occur. With iodine the proto- 

 plasm which lines the cell-wall becomes yellow, and the complete 

 absence of starch is also determined by this test. The large nuclei 

 of thes e cells are also clearly shown when water-eosin is applied. 

 These nuclei lie in the peripheral protoplasm and with the increase 

 ln size of the sap vacuole, the nucleus flattens out against the cell- 



wall in the thin layer of protoplasm remaining. Finally, the 



Goebel, K. Pflanzenbiologische Schilderungen I : 203. 

 t Strictly a tuber is a stem, or branch ; I have used the word here in a lax sense. 



