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CONTRIBUTIONS FROM THE SHAW SCHOOL, OF BOTAnV. 

 Xo. 8. 



On the Seed-Coats of the Genus Euphorbia. 



By L. H. Pammel. 

 (Presented January sth, tSgi.) 



To systematic botanists this genus otters many difficulties,, 

 and, though elaborated by careful and painstaking workers, the 

 obstacles have not been entirely removed. Who has not been 

 perplexed by £. maciilata and E. humistrata? The work of 

 Trecul and others on the stems of many plants,* of Engelmann 

 on the leaves of Conifers, &c., has shown that it may be possible 

 to utilize histological characters in classification, while it is al- 

 ways well enough to show some of these even if they are not 

 directly useful in this way. It was for the latter reason that this, 

 work was undertaken during a short vacation spent in St. Louis 

 a year since, though I had at the same time a hope that some- 

 thing might be learned of use in systematic botany. Owing to 

 other labors, I have not been able to present my paper earlier, 

 (although the work was substantially completed before my re- 

 turn from St. Louis), but a short account of the results was given 

 at the Indianapolis meeting of the American Association in Au- 

 gust last.^ I am under obligation to Professor Trelease for the 

 use of some authentic seeds from the Engelmann herbarium and 

 for other favors, and to Mr. A. S. Hitchcock for a few seeds.. 

 My drawings were transferred to stone by Miss Hoke and Mr. 

 Griffiths. To each I express my thanks. 



It is well known that the character of the seed is used to se- 

 parate some of the species of Euplioi-bia. Thus in E. poly- 

 gonifolia and E. Geyeri the seeds are smooth and even. In E. 

 maculata and E. glyptosperma they are minutely roughened. 

 In E. hexagona they are tuberculate. While these external dif- 



* Ferd. Pax has published an extended paper on the Anatomy of Euphorbiacese : .Die 

 Anatomic der Euphorbiaceen in ihrer Beziehung zum System derselben. Separate from 

 Engler's Botanische Jahrbiicher, vol. v., p. 384-421, PI. vi. ct vii. 



1. Read before Section F. 



