68 T. Holm — Erkjenia bulbosa. 



visible in the pericambium itself, just outside each of the two 

 oldest vessels, hence diametrically opposite each other. The 

 center of the root is occupied by a very wide vessel. If we 

 compare this structure of a lateral root with that of the fili- 

 form, primary root of the seedling, we notice the same arrange- 

 ment and development of tissues with the single exception 

 that there is no central vessel in the primary root, but the two 

 rows of vessels are separated from each other by conjunctive 

 tissue. The primary and the lateral roots thus show the same 

 principal structure and, as we have stated above, none of the 

 tissues showed signs of contractility. 



Fig. 5. Transverse section of the inner part of a lateral root of Erigenia. 

 E = endodermis ; P = pericambium; D = the ducts, developed in the pericam- 

 bium. There is a group of leptome on each side of the diametrically arranged 

 vessels, separated from these by a layer of conjunctive tissue, x 560. 



If we, now, examine a series of sections, taken from various 

 parts of the tuber itself (the seedling-tuber), we observe the 

 following modifications. In sections taken from a little above, 

 where the filiform root begins, the structure is identical as far 

 as concerns epidermis, cortex and endodermis, the two latter 

 however, containing deposits of starch. The pericambium, 

 on the other hand, shows a number of cell-divisions and con- 

 sists, thus, of several layers, surrounding the two rays of 

 hadrome and the leptome, situated as described above. In 

 other sections taken from the thickest part of the same tuber, 

 the structure is still more different, but illustrates, neverthe- 

 less, a root-structure. Epidermis, cortex and endodermis are, 

 still, preserved, but the endodermis surrounds now a mass of 

 parenchyma, filled with starch, which borders inwards on sev- 

 eral strata of cambium, which lies close to a central group of 

 vessels, arranged in a line, just as we observed in the filiform 

 root. There is no pith, and the leptome shows the same posi- 

 tion as before, but is separated from the vessels by the cambium. 



