TORREYA 



Vol. 10 



June, 1910 



No. 6 



NOTES ON THE GENUS SAMBUCUS * 



By T. D. a. Cockerell 



There has recently appeared t a very interesting review of the 

 genus Sambuais, by Fritz Graf von Schwerin, of Wendisch-Wil- 

 mersdorf, Brandenburg. It includes the species of the whole 

 world, discussing them from every point of view, giving maps to 

 illustrate distribution, and numerous figures, including a beauti- 

 ful colored plate of the fruits. The genus is divided into seven 

 groups; Ebulus, Eusambucus, Heteranthe.Scyphidanthe, Botryo- 

 Sambucus, Tetrapetalus, and Tripetalus. In the first five, the 

 corolla is five-lobed, in the manner normal for Caprifoliaceae ; but 

 the last two have it four- and three-lobed respectively. Tetra- 

 petalus has a single species, confined to Australia and Tasmania ; 

 while Tripetalus has also only one representative, exclusively 

 Australian. The austral distribution of these aberrant groups 

 has naturally suggested the idea that they are the oldest members 

 of the genus ; and this conception is illustrated in a phylogenetic 

 tree on p. ii, where Tripetalus appears as the stem-form, and 

 Tetrapetalus, as a lateral branch near the base. In Tripetalus the 

 fruits are golden-yellow, and hence it might be supposed that the 

 yellow mutations found in the northern species are atavistic. 

 There are, however, some reasons for doubting whether the 

 three- and four-lobed groups really are primitive. In the first 

 place, five lobes seems to be characteristic of the whole family 

 Caprifoliaceae, as well as related families. In the second, meristic 

 evolution usually proceeds by reduction, and it would seem, on 

 general principles, much easier to derive a three- or four-lobed 

 flower from a five-lobed, than the reverse. Finally, the most 



* Illustrated with the aid of the Catherine McManes fund, 

 f Mitt. Deutsch. Dendrolog. Gesellschaft. No. 18. 1909. 

 [No. 5, Vol. 10, of ToRREYA, comprising pp. 101-124, was issued May 26, 1910.] 



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