RANALES 429 



This reduction is well shown in the Magnoliaceae, Annonaceae, and 

 Winteraceae. Condensation of the flower has come about also by re- 

 striction of apical growth in the floral meristem, while growth continues 

 on the "shoulders" below. The Ranales show stages in this modification: 

 a flattened receptacle in Euponmtia and in the Monimiaceae (where 

 lateral expansion may be exaggerated); a slightly concave receptacle in 

 other families and a deeply concave one in Calijcanthus. In the 

 Ranunculaceae, evidence of the shortening of the receptacle is fre- 

 quently present in the form of a sterile vestigial tip between the carpel 

 bases. Where the carpel is solitary, the tip may be pushed aside in 

 ontogeny and the carpel take a falsely terminal position. 



Embryo and Endosperm. Embryo and endosperm types are remark- 

 ably constant throughout the order. The embryo is very small, often 

 undifferentiated at time of seed shedding, and is embedded in abundant 

 endosperm. After-ripening, in the form of morphological maturation 

 within the seed, is common in this order. (Coh/canfhus is an exception; 

 it has large, well-developed embryos and little or no endosperm in the 

 mature seed. ) 



Chromosome Number. Chromosome number varies considerably in 

 the order but seems constant for some families; 19 is apparently basic 

 for several families — Magnoliaceae, Cercidiphyllaceae, Trochodendra- 

 ceae, Tetracentraceae, Winteraceae; 14, for other families — Illiciaceae, 

 Schisandraceae, Eupteleaceae. 



Relationships within the Ranales. Morphology, even with the aid of 

 palynology, cytology, and serology, provides evidence of probable re- 

 lationships for rather few ranalian families. The totality of evidence 

 points, first of all, to the certainty that this order includes families with 

 more primitive characters than any other dicotyledonous order; sec- 

 ondarily, that these families represent several or many lines of evolu- 

 tionary development (Fig. 147), each represented by an individual 

 combination of primitive and advanced characters. Some of the lines 

 are represented by unigeneric families. The order appears to be an 

 assemblage of relic products of ancient stocks, held together by the 

 retention of many primitive characters. 



A few characters — pollen type, nodal structure, possession of "ethereal 

 oil cells," fasciculate stamens — seem important, but none of these can 

 be used alone to indicate relationship. 



Monocolpate pollen, together with pollen of types derived phylo- 

 genetically by modification of monocolpate pollen, characterizes the 

 families which seem to have the largest number of primitive characters: 

 Winteraceae, Magnoliaceae, Austrobaileyaceae, Eupomatiaceae, Himan- 

 tandraceae, Degeneriaceae. Tricolpate pollen and pollen of modified 

 tricolpate types characterize the Trochodendraceae, Tetracentraceae, 



