386 MORPHOLOGY OF THE ANGIOSPERMS 



as "stigma decurrent"; in other taxa, it is much shorter, and a series 

 exists in which the ridge is shortened and restricted to the distal part 

 of the carpel. The shortening is by progressive, acropetal fusion of the 

 carpel margins, and the remaining distal part of the stigmatic ridge 

 becomes pseudoterminal by a "hunchback," abaxial distortion of the 

 carpel. This shortened ridge seems to be the earliest "stigma," as a 

 restricted, distal, pollen-receiving area — earhest because accompanying 

 carpels that are hardly closed. 



The leaves are simple and pinnately veined. The wood stands apart 

 from that of most other angiosperms in the absence of vessels (Fig. 25). 

 In other characters also, it is of the type considered most primitive for 

 angiosperms. In ray structure, it is heterogeneous, with both uniseriate 

 and multiseriate rays, and the parenchyma distribution is diffuse. The 

 tracheids are long, with long-overlapping ends, and the pitting is fre- 

 quently scalariform. 



The centrifugal sequence in development in the androecium seems 

 to be an evolutionary advance over the more common centripetal order 

 and is surprising in the Winteraceae. The centiifugal sequence in the 

 Dilleniales and the centiipetal in the Ranales have been used as im- 

 portant characters in distinguishing these orders. But, in other general 

 characters, the Winteraceae resemble the other ranalian families far 

 more closely than the Dilleniales. The centrifugal sequence has prob- 

 ably arisen independently in these two orders. 



In the gynoecium, the Winteraceae show stages in the development 

 of syncarpy, a series from the free carpels of species of Drimys and 

 Bubbia, through the coherent carpels of Exospeiinum, to the syncarpy 

 of Zygogijnum. Syncarpy in angiosperm flower specialization is com- 

 monly considered a late step, associated with specialized carpels, but 

 connation is present even in this very primitive family. (It is present 

 also in Eupomatia and the MagnoMaceae—Pachylanmx.) In placenta- 

 tion, the Winteraceae show early stages in the transition from laminar 

 to submarginal. 



Morphologically, the most important specializations in the Wintera- 

 ceae are probably the transformation of the lateral stigmatic ridge into 

 the terminal stigma and the narrowing of the laminar stamen, with 

 transfer of sporangia to a near-distal position. In this evolutionary ad- 

 vance of the carpel, the stigmatic area is more favorably placed for 

 pollen reception. And, in the parallel advance, taking place at the same 

 time in the stamen, the microsporangia, sunken originally in the median 

 or lower part of the laminar stamen, are transferred to distal or termi- 

 nal positions and become protuberant. In this terminal position, dis- 

 persal of pollen grains is more free, whatever the agent. 



The history of the long pollen tube of angiosperms begins, at least 



