﻿The Histology of the Embryo of Indian Corn, 



W. W. Rowi.ee and M. W. Dohertv. 



( Plate 342.) 



The general appearance of the kernel of Indian corn is familiar 

 to every one. The embryo is literally at the base of the seed and, 

 on the side adjacent to the endosperm, has a shield-like expansion 

 of the hypocotyl — the scutellum — which has been interpreted usu- 

 ally as the cotyledon. There is a close coherence between the 

 tissue of the scutellum and the tissue of the endosperm. On this 

 account it is difficult to separate the embryo from the remainder 

 of the seed without destroying some of its tissue. A well-marked 

 layer of columnar epithelial cells, belonging to the scutellum, 

 separates the embryo from the endosperm. 



The axis of the embryo consists of the radicle, which is below 

 the point of attachment of the axis to the scutellum, and the 

 plumule, above the point of attachment. There is no obvious 

 hypocotyl. The radicle is completely encased in the coleorhiza 

 or root-sheath. Unlike many other grasses there is no epiblast 

 present in the embryo of corn. 



Calyptrogen. At the apex of the root is a distinct calyptrogen 

 from which by periclinal walls the root-cap is formed (fig. i). 

 The many-layered root-cap, in its younger, more internal part, con- 

 sists of parenchymatous tissue without intercellular spaces ; in the 

 older, more external parts, it is loose and in many respects de- 

 generated. The root-cap by its origin and development must be 

 considered a modification of the epidermal tissue system. 



Dermatogen. Immediately within the calyptrogen, occurs a 

 single row of cells somewhat elongated radially and with a thick 

 '^'ter wall. This is the dermatogen (fig. i), and is the formative 

 tissue of the epidermis. In the course of development the layers 

 resulting from divisions of the dermatogen exfoliate and the layer 

 °f the cortex, which functions as an epidermis, is designated an 

 epiblem. ■ 



i ribknt. This arises from a single laver, and indeed apparently 



(311) 



