Ramaley : HYPOCOTYL AND EPICOTYL IN WOODY PLANTS. 113 



short, unicellular hairs were seen, but none noted in very young 

 plants. There is a hypoderma of one or two layers of some- 

 what larger and thicker-walled cells. The rest of the cortex is 

 parenchymatous and large-celled. 



The endodermis consists of cells somewhat smaller than those 

 of the adjacent cortical layer. The endodermis was not recog- 

 nized in older material. Starch is present from the first in the 

 endodermis, pericycle and pith, but does not appear in the cor- 

 tex till nearly the close of the first season. 



The stele is at first quite small. There are four xylem bun- 

 dles arranged in pairs and four phloem bundles similarly dis- 

 posed. The phloem soon forms a complete ring, surrounding 

 the now considerably enlarged xylem bundles, which also even- 

 tually form a closed ring. 



Opposite each of the four original xylem bundles there ap- 

 pears in the pericycle a group of sclerenchymatous cells. 

 These groups become, at length, somewhat divided so that the 

 old hypocotyl may have a considerable number of smaller 

 groups. There are numerous sclerenchymatous fibers scattered 

 in small and large patches through the phloem and pericycle. 



The pith is thin-walled ; toward the end of the first season it 

 becomes lignified. The perimedullary zone, described by Flot 

 [1893], as an important feature of the stem structure is first 

 definitely noted at this time. 



The oleoresin canals described by Trecul [1867] as occurring 

 at the outer border of the pith, and by Van Tieghern [1884] as 

 in the inner xylem of the stem, were not distinguished in the 

 hypocotyl. Crystal rosettes of calcium oxalate occur singly in 

 certain cells of the phloem area. Single oleoresin cells are 

 found here and there in the cortex and phloem. 



Cork formation, as noted by Flot [1889 and 1890] takes 

 place in the layer of cells just below the epidermis. 



Structure of Epicotyl. 



The epidermis resembles that of the hypocotyl, but there are 

 numerous, somewhat long, curved or hooked epidermal hairs. 

 Most of these are unicellular. 



The hypoderma is, as previously described for the stem by 

 De Bary ([1884], p. 404), collenchymatous. The cells are 

 small ; toward the inside the hypoderma gradually shades into 

 the ordinary cortex. 



