914 TRANSACTIONS OP SECTION K. 



Alismacefe, Ranunculaceie, Magnoliaceffi, Polygonacero, &c. — trimery also occurs 

 in one foi-m or another; pentaraery i.s a later character derived by fusion of two 

 trimerous whorla accompanied by elision of a single member. 



The correct inteipretation of the Monocotyledonous group lies in the assigning 

 to it of an intricate annhinatioJi of primitive and reduced characters. 



Monocotyledons and Dicotyledons run into each other at all points, and are 

 intimately allied. They both .spring from a common ancestor, aud it is the 

 characters of this latter to which the foregoing remarks ap^jly. 



2. A N^ote on the MurphoJogjj of Endosperm. 

 By Professor H. H. W. Pearson, Sc.D. 



The origin of the Welwitschia endosperm from the fusion of potentially 

 sexual nuclei was briefly described. 



Such an endosperm is morphologically distinct from the prothallus of the 

 lower gyranosperm. It is proposed to distinguish it by the term ' trophophyte.' 



Th« relations between the trophophyte of Welwitschia and the endo.sperm of 

 the angiosperm were discussed. 



3. The Primary Wood of Lepidodendron and Stigmaria. 

 By Profisso'r F. E. Weiss, D.Sc. 



The primary wo id of Lejiidodendron, like that of most Lycopodiales, shows 

 a centripetal development, the protoxylem elements being found in definite 

 groups at the periphery of the stele. In some cases, e.y., in Lejndodemlron 

 fsnotense, figured by Renault, and in L. Fttiyciireyi.se, recently described by 

 Kidston. the stele is com])Osed of a solid mass of wood (protostele), while in one 

 form at least, L. selayinoides, the woody mass at the centre is interspersed with 

 iiarenchyniatous elenients, a condition of things which may well have led on to 

 the typical siplionostele such as is found in L. JIarcuyrfii. 



As is well known, the typical »SY(V/w(rtr'«, the underground organ supporting 

 the Lepidodrendron-stem, "po-sesses a siplionostele with centrifugal primary 

 wood, a condition which it is dilficalt to imagine to be primitive. At the York 

 meeting of the Association, at which I described a Stiyntaria with centripetal wood, 

 similar in some respects with Kenault's Stiymaria Brurdi, I .suggested that the 

 c^ntrifunal wood so typical of Stigmariie might have been developed by a reduction 

 of the older centrifugal wood and a substitution of the centripetal primary wood, 

 on the analoo-y of the ' new ' and ' old ' wood in the CycadoHlices and Cycadales. 

 lUit while the occurrence of ytigmariiB with centripetal primary wood supports 

 tills theory, a recently discovered Stiymaria seems to indicate that, in some cases 

 at all events, the normal stigmarian type of primary wood may have been 

 dirt'erently formed. In this Stiymaria, in which the stele is comparatively small, 

 tho'igh it shows a fair amount of secondary wood, the primary wood is centrifugal 

 in its development, but instead of surrounding a well-marked medulla, the 

 central area is filled with a mass of lignlfied elements resembling the protoxylem 

 aud narrow parencliymatous cells. The arrangement is in close agreement with 

 that found in L. xfdayinoides, except tliat the vascular elements of this central 

 area are lon^ and narrow instead of short and wide. '1 he stele would therefore 

 have to be described as a protostele of mesarch type, and by an increase of the 

 parenchymatous elements and a decrease of the vascular elements it would be 

 readily converted into a typical stigmarian siphonostele. The arrangement of 

 the primary wood in this new Stiymaria resemlAQS on an enlarged scale the 

 primary wood of the creeping stem of Selayinella ^pinulosa, or the hypocotyl 

 of S. Eraassiana, except for the admixture of parenchymatous elements amongst 

 the protoxylem. It is interesting to note that already, before the discovery of 

 this new specimen, Dr. Scott had drawn attention to the fact that these two 



