41] Phylogenetische Physiologie. 108 i 



all members of both groups have parallel veined leaves. The double bündle 

 also appears in seedlings of certain angiosperms, bxit this series has otherwise 

 departed very widely from its palaeozoic ancestry. 



A tbird line from our ancient stock gave rise to tbe cycadlike Bennel- 

 titales which flourished in the Cretaceous. The foliar trace here was a Single 

 bündle — either the primitive single Strand, perbaps comparable to that of 

 Medullosa, or a fusion of two — wich developed in the petiole and blade intO' 

 a series of typically exarch bundles with centrifugal secondary wood. The 

 reproductive organs were very specialized, and the group has probably given 

 rise to no living family of plants. 



The modern Cycadales perbaps constitute a fourth line from the palaeozoic 

 plexus which, however, lies very close to that of the Bennettitales. They 

 have often been coQsidered as derived from forms related to the Lyginoden- 

 dreae, but the exarch structure of the leaf bundles and the construction of 

 the seed, which is much more comparable to that of Medullosa than to that 

 of Lyginodendron, raake it very improbable that the latter genus has given 

 rise to the modern family. The cycads are also separated from the Bennet- 

 titales by the possession of a double leaf trace and a simple reproductive 

 System. The parallel venation of the leaf suggests the Cordaitales, and, as 

 we haveremarked above, Nüssonia shows an intermediate condition betvveen 

 the two types of leaf. 



It seems probable that the group arose in the late Carboniferous from 

 cycad-ferns possessing a double exarch leaf trace and petiolar bündle, a type 

 of leaf intermediate between the ordinary fern frond and the parallel veined 

 cordaitean condition, and a seed resembling that of Medidlosa. 



There are thus apparently two main groups in the exarch series, one 

 of which has progressed toward the coniferous type, and is represented by 

 the Cordaitales, and the modern Coniferales, and the other of which has 

 produced the cycadean type, as represented by the Bennettitales and the 

 modern Cycadales. 



147. Eames, A. J. On the origin of the herbaceous type in the 

 angiosperms. (Ann. of bot, XXV, 1911, p. 215—224, Taf. XIV.) 



Die herrschende Ansicht bezüglich des Ursprungs des soliden Holz- 

 zylinders der Angiospermen ist, dass er aus der Verschmelzung einer Gruppe 

 von ursprünglich getrennten Bündeln entstanden ist. Der Verf. verficht dem- 

 gegenüber mit Jeffrey und ßailey zusammen die Theorie, dass der solide 

 Holzzylinder das Ursprüngliche gewesen ist. Die vorliegende Mitteilung ist 

 m wesentlichen eine Zusammenfassung der bisher zugunsten dieser Ansich 

 bekannt gewordenen Tatsachen. An neuen Beobachtungen werden einige 

 Fälle von Durchbrechung des Holzzylinders an den Rhizomen von Potentüla, 

 Sanguisorba und Geum geschildert. 



148. Bailey, J. W. The relation of the leaf-'trace to the for- 

 mation of compound-rays in the lower Dycotyledons. (Ann. of bot., 

 XXV, 1911, p. 225—241. Taf. XV— XVII, 1 Textfig.) 



Durch Beobachtungen an Wundhölzern war der Verf. schon früher zu 

 dem Schluss gekommen, dass die breiten oder primären Markstrahlen durch 

 Verschmelzung von einreihigen Markstrahlen entstanden seien. Diese Theorie 

 stützt er in der vorliegenden Arbeit durch Untersuchungen an normalen 

 Hölzern. Zunächst schildert er, wie innerhalb der Gattung Almis sich all- 

 mähliche Übergänge von Hölzern mit ausschliesslich einreihigen Markstrahlen 



