350 TRANS. ST. LOUIS ACAD. SCIENCE. 



pean species which have been studied,* or by the abortion of one 

 of the sexes. Dissemination of the ripened seeds is effected by 

 birds which eat them for the sake of the fleshy colored aril, ulti- 

 mately disgorging the uninjured seeds, according to Huth.f The 

 mechanism by which weakly twigs are cast oft' (as in poplars, 

 elms, willows, and many other woody plants), is described by 

 von Hohnel in a comprehensive study of the subject.; 



PachysHma is represented only by our two species, one of very 

 narrow geographical distribution ; the other showing more clear- 

 ly the arctic-alpine character of the genus. No biological obser- 

 vations on either species have come to my notice. 



Celastrus^ represented in our flora by the single common form, 

 comprises some i8 or 20 species, largely of India and eastern 

 Asia. Like Euonvmus^ this genus was represented in Tertiary 

 times by many more species than at present. Lesquerevix de- 

 scribes three North American species from the Green River Ter- 

 tiary ; and Ward§ refers here 7 new species of the Post-Cretaceous 

 Laramie formations. The pollination of the flowers of C. scan- 

 dens is briefly discussed by Sprengel.|| Dissemination is eflected 

 by birds attracted by the aril, as in Euonyinus ; and, as in that 

 genus, the contents of the seed are protected chiefly by a single 

 layer of sclerotic cells. 



Maytenus^ a genus peculiar to the American continent, in- 

 cludes about 50 species, with a maximum development in the 

 tropics, from which a number of species reach into temperate 

 South America, while only one comes into the flora of our warmer 

 region. Several Tertiary species referred to this genus occurred 

 in more northern parts of the old world. Nothing is known to 

 me of the biology of our existing representative of the genus. 



* Cf. Darwin: Different Forms of Flowers, 2S7 (sexual relations of E. Europieus). 

 Delpino : Ult. Oss. ii. (2), 300, 302, Just, 1875, SS3, SjS (fetid odor of E. verrucosus, agency 

 of Diptera, &c,) Fournier: De la Fecondation dans les Phanerogames — Thesis, Paris, 

 1863, — 118 (protandry). Mueller: Befruchtung der Blumen (1S73), 153; and English trans- 

 lation (£. Europceus) , 



f Kosmos, X. 279, 287; Verbreitung der Pflanzen durch die Excremente der Thiere, 11. 

 On the structure of the protective seed-coats, see Weiss: Allgemeine Botanik, i. ^rf^Just, 

 187S (I), 31. 



X Mittheil. forstl. Versuchswesens fur Oesterreich, Heft 3; Just, 1S7S (1)1 91- 



§ Bull. U. S. Geol. Survey, No. 37, 1SS7, 77. 



II Entdeckt. Gerheimniss der Natur, 131. 



