REFERENCES 91 



xylem and metaxylem drawn from macerated primary xylem of 

 the liypoeotyl of the bean seedling. 



2. Outline, on a large scale, the form of a single vessel ele- 

 ment from the macerated primary xylem of Pteridmm, indicating 

 by horizontal lines the pattern of scalariform bordered pits on the 

 lateral walls. Draw, as seen under high magnification, a scalari- 

 form perforation plate of one of these tracheary elements. 



3. Prepare drawings of spring and summer tracheids of 

 macerated pine wood, showing the type and arrangement of the 

 pits as seen in face and sectional view. For comparison, draw 

 a single tracheid from macerated oak wood. 



4. Make drawings of vessel elements of macerated wood of 

 Liriodendron (or Bctida), QnercKs and Ciicnrbita, to illustrate 

 differences in the form of the elements and the type of perfora- 

 tion. Fill in the pits on a small portion of the lateral wall of each 

 vessel element. 



5. Summarize, in tabular form, the various types of cells 

 observed in the specimens of paper studied. Indicate whether 

 differences in the kinds of tracheary elements observed can be 

 used to deduce the source of the paper in each case, i.e., from 

 conifer or angiosperm wood. 



6. Prepare a' resume, based upon the conclusions of Jeffrey, 

 Brown (1918) and Bliss (1921) of the evolutionary development 

 of the vessel in seed plants. 



REFERENCES 



1. Bailey, I. W., and Thompson, W. P., Additional Notes upon 

 the Angiosperms, Tetracentron, Trochodcndron and Drimys 

 in which Vessels Are Absent from the Wood. Ann. Bot. 

 32:503-512. 1918. 



2. Barkley, G., Differentiation of Vascular Bundle of Tricho- 

 santhes anguina. Bot. Gaz. 83 :173-184. 1927. 



3. Bliss, M. C, The Vessel in Seed Plants. Bot. Gaz. 71 :314- 

 326. 1921. 



4. , , The Tracheal Elements in the Ferns. Am. 



Jour. Bot. 26 :620-624. 1939. 



5. Brown, F. B. II., Scalariform Pitting a Primitive Feature in 

 Angiospermous Secondary Wood. Science 48 :16-18. 1918. 



6. Cheadle, V. I., The Occurrence of Vessels in the Monocotyl- 

 edonae, Amer, Jour. Bot. 26. Supplement p. 9s. 1939. 



