394 MORPHOLOGY OF THE ANGIOSPERMS 



seem unrelated and can hardly be considered as indicating relationship 

 between the Magnoliaceae and Annonaceae on the one hand, and the 

 Calycanthaceae on the other. In Cahjcanthiis, the cortical system, con- 

 tinued from the peduncle and stem below, is used up in supplying the 

 lowest perianth parts; it does not continue in the receptacle, supplying 

 higher organs, and does not unite upward with the vascular stele of 

 the receptacle, as does the cortical system in the Magnoliaceae and 

 Annonaceae. 



The patterns of the cortical systems of the Magnoliaceae and An- 

 nonaceae are, however, much alike. The system in the magnolias is 

 anatomically more complete and seems better developed. Two opinions 

 have been expressed as to the relationship of the cortical systems in 

 these two related families. One interpretation of the annonaceous pat- 

 tern is that it represents a simplified reduction form of the more com- 

 plex and better-developed magnoliaceous type; the other interpreta- 

 tion of the pattern in the Annonaceae is that it is an early stage in the 

 elaboration of a cortical system, still incomplete and "unsettled" in pat- 

 tern. The Annonaceae are, in several characters, the more advanced 

 family, and it seems more likely that the cortical system is, in part, 

 vestigial, modified in relation to the simplification of the flower, espe- 

 cially of the perianth and gynoecium. Studies of the cortical systems in 

 the advanced and simpler genera of the Magnoliaceae should give evi- 

 dence in support of one of these theories. 



Among the important aspects of the morphology of the Annonaceae 

 and Magnoliaceae, is the variety in microsporangial position. The Mag- 

 noliaceae seem to show a series in progressive change in the position 

 of these sporangia from adaxial to lateral to abaxial (Liriodendron); 

 the Annonaceae have abaxial sporangia. These related families perhaps 

 provide evidence of the primitive position of the microsporangia, a 

 major, but neglected problem in the morphology of the angiosperms. 

 Apparently basic abaxial position is present only in primitive families — 

 Degeneriaceae, Himantandraceae, Winteraceae, Lactoridaceae, Annona- 

 ceae, Ceratophyllaceae, Chloranthaceae, Lardizabalaceae — families that 

 have many primitive characters and stamens of laminar or sublaminar 

 type, with prominent, sterile distal part. Dehiscence in stamens with 

 abaxial sporangia is, of course, extrorse, but it is difficult to determine 

 whether extrorse dehiscence in higher families represents survival of a 

 primitive type or is secondarily derived from introrse, as it appears to 

 be in Liriodendron. 



The Magnoliaceae and Annonaceae resemble one another in so many 

 ways that the two families must be closely allied — doubtless derived 

 from the same ancestral stock, with the Annonaceae more advanced in 

 some characters than the Magnoliaceae. The Annonaceae perhaps repre- 



