et 
NE\ 
BOT ANICÇAL 
GARDE 
The origin of the vascular structure in the genus 
Botrychium; with notes on the general anatomy 
by 
L. G. M. BAAS-BECKING 
from the Department of Botany, Stanford University, California 
L Introduction. 
Stelar Theor y. 
Any investigation of the origin of the vascular structures of 
a plant necessitates nowadays a consideration of certain assump- 
tions involved in the so-called stelar hypothesis. These assump- 
tions are based upon the theory of Ph. van Tieghem (32), 
but have been much modified and elaborated during the past 
three decades. 
The original hypothesis of van Tieghem however, has be- 
come an axiom for most recent investigators, and nowadays 
nearly every publication begins with the tacit assumption of 
the validity of the stelar theory. Because of the large range 
of variation in the vascular structures in the Pteridophytes, the 
investigators have confined their attention chiefly to these 
plants. 
Ontogen y. 
AN study of the young sporeling of different ferns has been 
undertaken in connection with the stelar theory, but most of 
the investigators were a priori convinced of the applicability of 
this hypothesis (exceptions, Campbell (9), Brebner G), 
West (42)), and did not study therefore the origin of the vas- 
Recueil des trav. bot. néerl. Vol. XVIII. 1921. 22 
