Rama ley : iiypocotyl and kpicotyi. in woody plants. 95 



time. It cxcnliially appears in the pericycle, phloem, meduHary 

 rays and inner elements of the xylem. 



The stele is originally very small. In the disposition of the 

 vascular tissues this plant differs from all others examined by 

 the writer. In cross section the center of this stele is seen to 

 be occupied by an elongated area of xylem. On each side of 

 this, separated by a small amount of conjunctive tissue, is a 

 crescent-shaped mass of phloem. The xylem soon forms a 

 somewhat four-sided mass, and is surrounded by a ring of 

 phloem. The xylem at length becomes circular, and the sur- 

 rounding phloem increases greatly in amount. 



There is but slight development of stereom, although, toward 

 the close of the first season, numerous isolated sclerenchymatous 

 elements are found in the phloem. 



The cork cambium originates in the endodermis or pericycle. 

 The ring of phellogen is sometimes irregular, appearing now 

 in one, now in the other of the regions named. 



It may be said that, since the structure of the hypocotyl in 

 this species so much resembles the general type of root struc- 

 ture, it was thought best to examine a large number of plants, 

 lest the peculiarities noted should have been due to teratological 

 development. All the plants were, however, found to be alike. 

 Neither is there any trouble in this species, to determine the 

 lower limit of the hypocotyl, for it is enlarged below and does 

 not gradually shade off into root, as is the case in some seed- 

 lings. 



Strticttire of E^icotyl. 



The epidermis is small-celled. There are numerous simple, 

 blunt and pointed hairs, and also some with a single stalk cell 

 and a multicellular bulb at the distal end. 



A somewhat collenchymatous hypoderma is developed, con- 

 sisting of two or three layers of cells, which are smaller than 

 the deeper cells of the cortex. 



The small-celled endodermis, at first distinct, soon becomes 

 displaced and changed, owing to secondary growth of sub-lying 

 tissues. 



Starch is almost entirely absent, except in the endodermal 

 region, till about the close of the first growing season, w^hen it 

 appears in the pith, medullary rays, phloem and, to a slight 

 extent, in the cortex. 



