1892.] NEW-YORK MICROSCOPICAL SOCIETY. 87 



of the successive rings of thickening in the older zones of the 

 secondary bast. From examination of many sections taken from 

 stems varying in age from four to twenty-five years, it seems im- 

 possible that the conclusions of the authors mentioned can be 

 correct. The law may be true for the lians, with which they 

 chiefly worked, and it is possible that the IVistarta, under differ- 

 ent conditions of climate and soil, may conform to the above law. 

 The cortical sheath of the Wistaria gives an unmistakable land- 

 mark by which to locate growth. This is always near the peri- 

 blem and plerom boundary. No amount of it is found in any 

 other place. If De Bary's position were true this sheath could 

 never appear in the phloem that has been cut off externally by 

 wood. It would ever be pushed out with the periblem by the new 

 growth. But not a section of the interstratified phloem has been 

 examined that does not reveal the cortical sheath on the periphery 

 of th© bast. It may be advanced that with the formation of the 

 new cambium dilatation of the adjoining parenchyma and sclero- 

 sis follow. In this case the process could easily be noted, and, 

 secondly, the dilatation would present features distinct from that 

 manifest in stems where growth is yet normal. As a matter of 

 fact, the structure of the included bast zones differs in no respect 

 from that of the regular growth. The same widening of the 

 medullary ray, and the completed sclerosis, etc., are always pre- 

 sent. Again, in sections taken from the angles formed by the 

 commingling of two bast zones, the sclerosis is seen to curve 



Kxplaiiatloii of Plate 35. 



Fig. 3. Cross-section of pith, showing flbrovascular bundle, A, in the medullary 

 sheath, x 200.— Fia. 4. Radial section of pith. A, spiral tracheids. x 200.— Fig. 8. 

 Cross-section of sylem, showing A, autumn growth, and B, denser wood. X 500.— Fig. 9. 

 Tracheid with anastomosing spirals, x 500.— Fig. 10. A, longitudinal section of tracheae, 

 showing forms of pits and canals ; B, transverse view, showing the thickening portion 

 encroaching upon the slit-like canals, x 500.— Fig. 11. Cross-section of liber fibres, 

 showing stratification, x 500.— Fig. 12. Liber fibres separated by maceration, x 66.— 

 Fig. 13. Bast fibres separated by maceration, x 66.— Fig. 14. Bast fibre*, cross-section 

 showing two layers, x 500.— Fig. 15. Three sacks of the crystal fibre swollen by mace- 

 ration, x 5(30.— Fig. 10. Crystal forms. X 500.— Fig. 17. Cross-section of inner and 

 outer cortex, showing the dilatation of the medullary ray. The heavy horizootal lines 

 and the dotted spaces represent the relative amounts of parenchyma in the bast, x 12. 

 —Fig. 18. Plastids and starch granules, x 500,-Fig. 19. Cross-section of stem, show- 

 ing the cork meristem in the third layer of cells, and the epidermis with trichome, E. 

 >: 300.— Fig. 20. Cross-section of cork cells. A, A, the much-thickened cells ; B, those 

 completely suberized. x 500.— Fig. 21. Short sclerenchyma. x 500.— Fig. 22. Stoma 

 of stem. X 30i?.— Fig. 23. Lenticle. A, A, tabular cells radially joined to retam ia 

 place the loose cells ; C, phelloderm. x 200. 



