pliyllotaxy, the third leaf-scar, starting at any point, is directly over the 

 first; in the second, or two-fifths pliyllotaxy, the sixth leaf-scar is over 

 the first; while in three-eighths pliyllotaxy, the ninth is directly over the 

 first, that is, there are eight leaves in a cycle, which consists of a spiral 

 passing three times around the stem. The pliyllotaxy may vary from 

 two-fifths to three-eighths in the same species or even in different twigs 

 on the same plant. 



The lateral buds are usually single but there may be two or more in 

 the same axil, one above another, when they are superposed. The term- 

 inal bud in many cases is not present, the upper lateral bud taking its 

 place and pushing aside a terminal scar, which may be caused by the fall- 

 ing off of an inflorescence, but usually (according to Foerste, Bot. (iaz. 

 xvii. No. 6,) is due to the casting off of the green terminal portion of the 

 twig earlier in the season. 



Since it has not been necessary, except in a few cases, to discrim- 

 inate between closely allied species, the descriptions do not include the 

 finer details but are confined to what seemed sufficient to identify the 

 species. 



The list includes sixty-three native species and four that are in com- 

 mon cultivation and have escaped in places. The four not native are 

 Tree of Heaven, Black Locust, Catalpa and Osage Orange. 



The fruit or leaves are often obtainable and will aid in the identifica- 

 tion, in which case the student should refer to Gray's Manual. 



Thanks are due to Dr. William Trelease, Director of the Missouri 

 Botanical Garden, and Prof. S.C. Mason, of this College, for various favors. 



