Ramaley : HYPOCOTYL AND EPICOTYL IN WOODY PLANTS. 131 



cccidentalis^ Broussonetia papyrifera, Liriodendron tulipifera, 

 Menispermum canadcnse, Gleditsia triacanthos, Robinia pseu- 

 dacacia, Ptelea trifoliata, Ailanthus glandnlosa, Rhamnus 

 purs/iiana, Catalpa spcciosa, Cephalanthus occidentals. 



Comparison of Cortex of Hypocotyl and Epicotyl. The 

 cortical cells of the hypocotyl are nearly always much larger 

 than those of the epicotyl. This is so commonly the case 

 that various species need not here be specially mentioned ; a 

 good example is Parkinsonia aculeata. The cortex of the hy- 

 pocotyl is thicker than that of the epicotyl. 



Comparison of Endodermis and Pericycle in Hypocotyl and 

 Epicotyl. The endodermis in the hypocotyl is, as a rule, more 

 distinct and persists longer than that of the epicotyl. Its cells 

 contain starch. Pericycle is well developed in the hypocotyl, 

 usually consisting of two or more layers of small cells. 



Typical Structure of the Stele of the Hypocotyl. The stele 

 is usually somewhat quadrangular. As a rule there are four 

 phloem bundles and four xylem bundles. The phloem and 

 xylem may be in contact or they may be separated by a small 

 amount of un differentiated parenchyma. In the latter case 

 each phloem area is either directly outside of a xylem area 

 (when the phloem may be spoken of as opposite the xylem), or 

 the phloem bundles are removed from the xylem by greater or 

 less angular distances (alternate arrangement). Using the 

 foregoing terminology the arrangement of bundles may be de- 

 scribed as opposite in the following : Liriodendron tulipifcra, 

 Menispermum canadense, Butneria jlorida, Cercts canadensis, 

 Amorpha fruticosa, Ptelea trifoliata, Ailanthus glandulosa, 

 Schinus molle, Berchemia racemosa, Rhamnus purshiana, Vitis 

 cordifolia, Cephalanthus occidentalis. It is alternate in Eu- 

 calyptus globulus and Tecoma radicans. 



Certain modifications of the more usual type just described 

 would best be noted separately. There are four xylem bundles 

 and eight phloem bundles in Robinia psetidacacia. In Parkin- 

 sonia aculeata, Gleditsia triacanthos and Elaagnus umbellata 

 there are eight xylem bundles and four phloem bundles. The 

 xylem bundles soon fuse together in pairs in the last two named 

 species. In Celtis occidentalis and Toxylon pomiferum, the 

 phloem forms two crescent-shaped areas while the arrangement 

 of the xylem is normal. 



Unusual Structure of the Stele of the Hypocotyl. In certain 



