RAN ALES 431 



Magnoliaceae, surely close to the Annonaceae, do not have this type of 

 endosperm. 



The absence of vessels in the wood was at one time used as a basis 

 for the setting apart of the taxon Homoxyleae. It has become apparent 

 that this character is valueless in phylogenetic considerations, but that 

 stages in the evolution of the vessel, when used together with other 

 characters showing stages in evolutionary advance, are important. In 

 the Ranales, the presence of scalariform vessels in most families and 

 the existence, within the order, of stages in the reduction in number of 

 bars and in the increase in size of the perforations are outstanding 

 characters. Simply perforate vessel elements are present in the 

 Lactoridaceae, Calycanthaceae, Ranunculaceae, Annonaceae, Berberi- 

 daceae, Lardizabalaceae, Himantandraceae, Lauraceae. The inclusion 

 in this list of advanced ranalian families of the more primitive 

 Lactoridaceae and Himantandraceae is an example of the unequal ad- 

 vance in rate of specialization in flower and vascular anatomy. Simply 

 perforate vessel elements are present also in the aquatic families 

 Nymphaeaceae, Cabombaceae, and Ceratophyllaceae, in which the vas- 

 cular tissues are highly specialized. In these families, reduction has 

 doubtless removed much evidence of relationship, and no affinities with 

 other families are apparent. Ceratophtjllum perhaps does not belong in 

 the Ranales, though its stamens seem to place it there. The supposed 

 resemblance of the gynoecium of Nehimho to that of Eupomatia is in 

 error; the carpels in Eupomatia are intimately connate, not sunken in- 

 dividually in the receptacle, as commonly described. 



A possible correlation of basic chromosome number with nodal struc- 

 ture has been suggested. The genera studied that have tri- or multi- 

 lacunar nodes — in the Winteraceae, Magnoliaceae, Trochodendraceae, 

 Tetracentraceae, and Cercidiphyllaceae — have 19 small, short-rod-like 

 chromosomes; the genera studied which have unilacunar nodes — in the 

 Illiciaceae, Schisandraceae, and Eupteleaceae — have 14 much larger 

 chromosomes. But differences in chromosomes, as shown in illustrations, 

 are not sufficiently clear, and the nature of some of the unilacunar 

 nodes — primitive or derived from trilacunar — is uncertain. 



The Ranales show a variety of important ancestral characters: the 

 primitive flower form — bisexual, polymerous, without perianth, ap- 

 pendages spirally arranged; stamens laminar, with sporangia paired, 

 medianly placed, wall-less, and embedded in the sporophyll; mega- 

 sporangia with multicellular archesporium embedded in projections of 

 sporophyll tissue (ovules); vesselless xylem and fiberless phloem; uni- 

 lacunar nodes, with two traces. Associated with these primitive char- 

 acters and scattered among the various families are many of the most 



