204 Cephalotaxus, 



abgeworfen, wenn sich die Suspensoren etwa zu der in Fig. 123, 40 an- 

 gegebenen Länge entwickelt haben. Die zweite Etage bildet den eigent- 

 lichen Embryo, die dritte die Suspensoren und die obere die Rosette. 

 Wenn die primären Suspensoren ihre größte Länge erreicht haben, 

 bilden sich die proximalen Zellen des Embryos zu sekundären Suspen- 

 soren um (Fig. 123, 44). Oft entstehen kleine sekundäre Embryonen 

 durch Sprossung aus dem Hauptembryo (Fig. 123, 43, 44). 



Der Gefäßbündelverlauf des Samens 



wurde von Worsdell in eiuem Artikel „The vascular structure of the 

 ovule of Cephalotaxus", Ann. of Bot., XIV, 1909, p. 137 untersucht. 



Im Arillus verlaufen zwei Gefäßbündel, eines an jeder Seite des 

 Samens, mit „inverted orientation", d. h. mit ihrem Xylem nach außen 

 und ihrem Phloem nach innen gerichtet, wie Strasburger nachwies. 

 Worsdell fügt hinzu: 



„As above stated there is a Single bündle on each side of the seed. 

 It is greatly extended in the tangential direction and situated on the 

 innermost side of the outer and in close proximity to the woody inner 

 integument. The secondary centrifugal xylem of the bündle is 2 or 

 3 layers thick. Besides this, however (and this is the point of my whole 

 note), well-developed centripetal xylem occurs, the tracheides 

 composing it extending along the whole tangential face of the centri- 

 fugal xylem in considerable quantity. A verj' interesting and important 

 point in connexion with this diploxylic structure is the fact that there 

 are two sets of protoxylem, as has been also shown for bundles of a 

 similar structure in the sporophyll of Cijcas, peduncle of Stangeria etc. 

 One of these protoxylems is attached to the centrifugal, the other to 

 the centripetal xylem. The significance of the fact is this: that it indi- 

 cates clearly, in my opinion, the derivation of a collateral bündle pos- 

 sessing such a structure from a concentric Strand of which the phloem, 

 which in the ancestors of the plant was attached to the outer side of 

 the „centripetal" xylem, has completely disappeared. This is also my 

 explanation of the occurrence of centripetal xylem elsewhere, as in the 

 peduncle of some Oycads, and the foliar organs of Cycads and Coni- 

 ferae. I regard Cephalotaxus as the most ancient of coniferous genera, 

 and therefore supposing the Coniferae to be derived from some ancient 

 Fernstock, we should expect to find it exhibiting characters in its 

 most primitive organs similar to those we find in Cycads and Ginkgo, 

 Now the two most primitive foliar organs of any plant are, to my mind, 

 thecotyledon and the ovular integument. In the former I have 

 already shown the absolutely Cycadean character of the structure of the 

 vascular bündle, with its enormously developed centripetal xylem. In the 

 latter a similar diploxylic structure of the bündle, as has been shown 

 above, also predominates. Two conclusions may be drawn from these 

 facts viz. (1) that Cephalotaxus is the most primitive of the Conifet'ae\ 

 (2) that this genus forms in some measure a connecting link between 

 Cycadeae and Coniferae, and helps us, to trace, however firmly, a 

 fragment of the line of descent in the latter group." 



Die Schwierigkeit liegt auch hier wieder in dem Umstände, daß 

 keine Pflanze ganz primitiv oder ganz fortgeschritten ist, sondern 

 neben primitiven Merkmalen sehr weit fortgeschrittene enthalten kann; 

 so primitiv, wie Worsdell will, ist Cephalotaxus wohl sicher nichts 



