Ramaley : iiypocotyl and epicotyl in woody plants. 131 



occidentalism Broussonctia papyri/era, Liriodendron ttilipifera, 

 Mcnisperrnum canadcnse, Gleditsia triacanthos, Robinia pseti- 

 dacacia, Ptclea trifoliata, Ailanthus glandtilosa, Rhamnus 

 purshiana, Catalpa spcciosa, Ccphalanthns occidcntalis. 



Comparison of Cortex of Iiypocotyl and Epicotyl. — The 

 cortical cells of the Iiypocotyl 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 aciileata. The cortex of the hy- 

 pocotyl is thicker than that of the epicotyl. 



Comparison of Endodcrmis and Pericycle in Iiypocotyl 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 undifferentiated 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, 

 Menisperniiim canadense, Butneria forida, Cercts canadensis, 

 Amorpha fruticosa, Ptclea trifoliata, Ailanthus glandulosa, 

 Schinus 7nolle, Berchemia racemosa, Rhamnus purshiana, Vitis 

 cordifolia, Cephalanthus occidcntalis. It is alternate in Eu- 

 calyptus globulus and Teconia 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 pscudacacia. In Parkin- 

 sonia aculeata, Gleditsia triacanthos and Elceagnus unibellata 

 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 occidcntalis and Toxylon pomifertcm, 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 



