306 Pteridophyten. 



gaps and the first trace originates from the sides of one of them 

 and is, theretore, like all the later ones double at its origin. In 0. 

 reticulatum the spikes are not, as Campbell states, provided with 

 bundles which can be traced in an adaxial position to the base of 

 the petiole; the five Strands of the spike arise marginally by suc- 

 eessive branchings. In the section Ophioderma the identity of the 

 margins of the leaf trace is often obliterated as we pass upwards. 

 In the weaker leaves of O. palmatum the leaf trace is widely open 

 adaxially; but as the plant increases in strength they approach one 

 another, tili in the fertile leaves there is a complete circle of Strands. 

 There are numerous fusions and the margins are already comple- 

 tely obliterated near the base of the petiole, a long way below the 

 spike. The vascular supply of the median spike comes off adaxially, 

 that of the two higher, lateral ones marginally. At the passing out 

 of the Strands into the spike a temporary commissure may be for- 

 med between the more marginal ones. The spikes have three bundles, 

 the middle one being the largest. 



The following theoretical conclusions are drawn: The spike of 

 Euophioglossum is to be regarded as the unit upon which develop- 

 ment has plaj^ed, leading by duplication, interpolation or in some 

 cases by chorisis or merely by distal branching to an amplification 

 of spikes. For this process the term pleiogeny is suggested. These 

 branchings are not to be interpreted in terms of pinnae as nor- 

 mally understood. At the same time the normal single spike of 

 Euophioglossum may ultimately be held to be of pinna nature, 

 perhaps in most cases the result of pinna fusion; butit is by pleiogeny 

 ol this spike that the condition found, for exemple, in O. palmatum 

 results. In 1896 the author expressed the view that the affinities of 

 the Adders' Tongues lay with the Lycopods and Sphenopbylls 

 rather than with the Ferns; the question is now reconsidered in 

 the light of subsequent contributions to our knowledge. Kidston 

 and Gwynne Vaughan's work tends to show that the Osmundaceae 

 are derived from protostelic Ferns and suggests an analogy be- 

 tween these Ferns and the Ophioglossaceae; Chryslers demon- 

 stration of the intramarginal origin of the vascular suppl3 T of the 

 spike favours the affinity with the Ferns rather than that with the 

 Sphenophylls. The abandonment of the similarity between the 

 Ophioglossaceae and the Sphenophylls founded on Rostowzew's 

 Observation of the disintegration of certain potential sporogenous 

 cells without undergoing the tetrad division, an Observation that 

 can no longer be maintained, also militates against the alliance 

 with the Sphenophyllales. The author is therfore inclined to accept 

 the affinit3 T of the Adder's Tongues with the Fern 's, but holds on 

 anatomical grounds that they have arisen from a type not unlike 

 the Osmundaceae by a progressively more bulky modification of 

 the leaf and sporangium. Their affinities would thus be rather in 

 the direction of the Botryopterideae and Osmundaceae. 



Isabel Browne (London). 



Bower, F. O., Studies in the Phylogeny of the Filicales. 

 I. Plagiogyria. (Ann. Bot. p. 423—450. April 1910.) 



Plagiogyria pycnocephala though little removed from solenostely 

 has a radial dictyostele. The leaf traces of the genus are mesoxylic 

 at their first origin, but owing to an indentation of the inner margin 

 of the metaxylem shifts right and left so that the trace soon appears 



