Harshberger : Water-storing tubers 273 





(a) taberosa and subspecies (p) ctuberosa. The regeneration from 

 tubers in N. cordifolia subsp. Uiberosa, in A 7 , hir sit tula, in N. Pluma, 

 and in N. philippinensis consists in the formation of stolons with 

 a central axial bundle system and normal green pinnae arising 

 from these ramentae-covered stolon-like branches. His photo- 

 graphic illustrations show the character of the various forms of 

 tubers in a very satisfactory manner. Incidentally, Heinricher 

 states that in N. cordifolia the tubers serve for the storage of 



water. In the large parenchyma-cells of the tubers of N. hirstt- 

 tula Heinricher found small starch grains (?), which in no case 

 completely filled the cells, and such cells reacted to Fehling's 

 solution, indicating the presence of sugar. Sperlich likewise claims 

 that he found the cells of young tubers filled with starch, while 

 in the mature tubers the starch grains were sparingly found, but 

 the sugar content had increased proportionately. 



My observations on the structure of fern tubers, now to be re- 

 corded, are at variance with the above statements in the two species 

 of Nephrolepis investigated by me, viz., TV. cordifolia and N. daval- 

 hoides. In these two ferns, the lateral cord-like branches with 

 small hair-like ramentae are brown in color (Plate 17, figure 2). 

 These ramentae extend also to the wrinkled surface of the tuber, 

 out are more sparingly found. A microscopic examination of the 

 tuber surface shows that it consists of large epidermal cells, the 

 walls of which interlock by sinuous lines (Plate i 7, figure 3). The 

 interior of the tuber is found to consist of large, rounded hexa- 

 gonal, or pentagonal parenchyma-cells, with thin walls (figure 4), 

 while the fibro vascular elements are arched near the surface, run- 

 n »ng from base to apex. These parenchymatous cells in the freshly 

 cut tubers are filled with watery protoplasm, and the observer is 

 impressed by the absence of solid reserve food. Considerable 

 Protoplasm with a large nucleus is present in the younger cells 

 (figure 5), but in the older cells the protoplasm and nucleus are 

 confined to a thin wall-layer, as the sap vacuole increases in size 

 I figure 6). Treatment with iodine fails to reveal the presence of 

 starch and protein. Water-eosin colors the protoplasm but slight- 

 ly, and this reaction, as also the application of Bismarck brown, 

 deludes the possibility of the presence of protein granules, while 

 e use of Fehling's test for sugar gives a decided reaction, if 



