Svensk Botanisk Tidskrift. 1922. Bd. 16, H. 2. 



ON THE GEOLOGICAL HISTORY OF THE 

 SCIADOPITINEAE. 



A PRELIMINARY NOTE 



BY 



RUDOLF FLORIN. 



That the genus Sciadopitys occupies a remarkably isolatcd posi- 

 tion wilhin the Tuxodineae, is eniphasized l)y sevcral aiithors as a 

 result of morphological, anatomical and cmbryological invcsligalions. 

 The vegetative system is built up ol' long shoots and short shoots, 

 in which respect this genus differs from othcr taxodineous genera. 

 The peculiar short shoots, which may be charactcrized as sym- 

 phyilods or double needles, give Sciadopitys an isolated position 

 among all otlier known recent conifers. According to my own 

 investigations, which I propose to publish in the ncar futurc, 

 Sciadopitijs dificrs from all recent gymnosperms with regard to tlie 

 structure of stomata. This structure is, according to the work of 

 l^ORSCH, of great phylogcnetic importance. Of the gymnosperm- 

 lype of stomata Pohsch also says: "Der Porus zeigt meist keine 

 Gliederung in Vorhof, Zentralspalte und Hinterhof, sondern ist sehr 

 niedrig, in verschiedener Höhc ziemlich gleich weit, scitcner in der 

 Mitte schwach erwcilert." Characteristic for the stomata of Scia- 

 dopitys are, however, a central porc and a "Vorhof", boundcd on 

 the outer side by two thin ridges or lamellae (fig. 1), which take 

 their origin from the two guard-cells and bend ovcr the stomatic 

 aperture in a very peculiar man ner. b\irther Sciadopitys is of 

 much interest with regard to embryoiogy. Lawson says: "On the 

 whole the embryo of Sciadopitys is rather uni([ue; il docs not I)ear 

 a close rescmblance to either the Atiietineae, Ciipressineae, or Ta.va- 



