NEW-YORK MICROSCOPICAL SOCIETY. 79 



THE ANATOMY OF THE STEM OF WISTARIA 



SINENSIS. 



BY CARLTON C. CURTISS. 

 iRead May 6M, i?92.) 



About a year ago Dr. N. L. Britton received a letter calling 

 his attention to the growth of the Wistaria sinensis, and asking 

 an explanation of the apparently anomalous development. Under 

 his direction some study has been given to the anatomical features 

 of the plant with a view to the solution of this question. A 

 gross examination of the anatomy of a transverse section of the 

 older stems (Fig. i) shows at once a deviation from the normal 

 growths of the phanerogams, but the deviation is not apparent in 

 the younger stems. In the latter the orientation appears normal^ 

 the products of the plerom, periblem, and dematogen being per- 

 fectly developed and presenting regular growth. For several 

 years, usually twelve or more, this continues, after which time a 

 new cambium zone is formed outside the primary bast and the 

 old cambium dies. Growth now continues normally for a series of 

 years, usually not more than eight. In all cases examined the dura- 

 tion of this secondary growth was several years less than that of 

 the primary. In time this secondary cambium dies and a new one 

 arises with the usual increase as mentioned above. This method 

 of development continues through life, stems twenty-five years 

 old showing four or more bast zones. In stems, however, which 

 have been subjected to pressure while growing and thus have had 

 their symmetrical development checked, the secondary cambium 

 zone appears at a much earlier age, even at the end of the fourth 

 or fifth year. 



Such are the apparent features of the plant. A microscopical 



Explanation of Plate 33. 



Fig. 1. Cross-section of a stem of Wistaria sinensis thirty years old, showing three 

 and portions of a fourth zone of bast.— Fig. 2. Cross-section of a six-year-old stem, 

 interlocked with other branches.— Fig. A. Stem twelve years old, showing the begin- 

 ning of the anomalous growth.— Fig. B. Same stem thirty centimetres below A, show- 

 ing complete formation of a new cambium.— Fig. C. Cross-section of a seventeen-year- 

 old stem, much twisted and compressed. All the figures natural size. 



