RAN ALES 411 



mostly with a prominent hypanthium of varied, even extreme, form. 

 The wood varies considerably in details of structure. The family has 

 been considered close to the Calycanthaceae on the basis that, in both 

 families, the hypanthium is greatly enlarged. But in other characters, 

 the families are not alike. Similarity in wood structure and in stamens, 

 which have lateral appendages and valvular dehiscence, suggests 

 relationship to the Lauraceae. The Monimiaceae perhaps form a link 

 between the Ranales and the Laurales. 



Amborellaceae 



The Monimiaceae were shown, in 1948, to contain a vesselless genus, 

 AmboreUa, a shrub endemic to New Caledonia. The morphological 

 characters are closelv similar to those of the Monimiaceae but differ 

 sufficiently to set AmborcUo apart from the other genera, as forming an 

 independent family. Though the flowers are unisexual, the perianth is 

 very primitive, with transition in spirally placed organs from bracteoles 

 to tepals. The stamens have a broad filament. The wood is highly primi- 

 tive: vessels absent; rays of the primitive heterogeneous type; tracheary 

 elements very long, resembling those of other vesselless taxa (Fig. 24). 

 The tracheary pitting is circular, occasionally scalariform. The nodes are 

 unilacunar. Pollen morphology supports the segregation of AmboreUa 

 as a separate family, the Amborellaceae. 



EUPTELEACEAE 



The relationships of Etipfclea, which has been placed in the Troch- 

 odendraceae and the Hamamelidaceae, have been difficult to deter- 

 mine. The genus shows some primitive characters; the bisexual flowers 

 have numerous free stamens, anthers with prolonged connective, and 

 long-stipitate carpels (Fig. 73S). But the wood, as compared with that 

 of Trochodendron, which is vesselless, has scalariform vessels; the 

 pollen grains are tricolpate or polycolpate. In nodal anatomy, a modi- 

 fied, unilacunar type, this family differs from all other woody ranalian 

 families. Euptelea is another isolated family with strongly contrasting, 

 primitive and advanced characters; its primitive flowers and wood are 

 ranalian, but the specialized pollen and nodal anatomy are not. It is 

 surely not close to the Hamamelidaceae. Eupfelca, with its peculiar 

 combination of characters, seems worthy of distinction as an inde- 

 pendent family. 



Ceratophyllaceae 



The morphology of CerafophijUum has received much study, but 

 there has been little agreement as to its interpretation or to the prob- 

 able relationships of the family. Like other aquatic taxa, it shows both 



