122 MORPHOLOGY OF THE ANGIOSPERMS 



pendage of the anther, an appendage that seems to be generally 

 functionless. (In one species of Magnolia, it is large and apparently 

 plays a part in pollination.) In the more advanced genera of the 

 Nymphaeaceae and in die Cabombaceae — Barclaija, Eunjale, Cahomha, 

 Brasenia — it is absent. 



The most prominent part of the reorganization in the specialization 

 of the anther is the change in position of the sporangia (Fig. 53). The 

 sporangia, remaining in pairs, are moved ("migrate," "slide") laterally, 

 so that they come to lie, first, obliquely lateral ("trapezoidal") (Fig. 

 54D), with dehiscence latero-introrse; then lateral, with dehiscence 

 latrorse (54L); and as a final position, halfway around the anther, ahax- 

 ial, with dehiscence extrorse (Fig. 55, 2, h-h). This positional change, 

 as exemplified by the Nymphaeaceae, has been likened to the "phyletic 

 slide" of sori in the leptosporangiate ferns. 



The positional changes in the sporophyll seem to involve all the 

 tissues except the midvein. The lateral veins are moved laterally and 

 around toward the opposite side, as are two of the sporangia. In the 

 Nymphaeaceae, the lateral veins have been described as "twisting and 

 rotating in their upward course" in the stamen (Fig. 55, 5, c-c, d-d). In 

 some taxa, some of these bundles in the anther are inverted ( Fig. 53D ) 

 or have united with others to form amphicribral or bicollateral forms. 

 Their course and orientation have been distorted during the more 

 or less massive differential growth. Similar inverted bundles have been 

 found in the stamens of Eiipomatia. This inversion of bundles in anthers 

 resembles that of the ventral bundles of carpels, but, in the carpel, there 

 is definite folding or rohing of the lamina and a chamber is enclosed; 

 that in the stamen is by massive differential growth, and no chamber 

 is formed. (Changes in the orientation of vascular bundles, including 

 inversion, are frequent in specialized petioles.) 



The course and orientation of the lateral veins of the stamens in the 

 Nymphaeaceae and Cabombaceae give strong support to the theory of 

 sporangium migration. In the laminar stamens, the vascular bundles 

 are distributed and oriented as in leaves, but, in stamens with narrow 

 filament, thick connective, and lateral sporangia, the outer bundles 

 are often obliquely oriented or inverted (Fig. 53). In Nelwnbo, the 

 highly specialized filament shows stages in the twisting and inversion 

 of the lateral veins. Accompanying this distortion in orientation is loss 

 of the weaker lateral veins (Fig. 55, 5). 



Progressive change in sporangium position from adaxial to abaxial 

 has been recognized as a feature of advancing specialization in the 

 anther. This change has apparently occurred independently in several, 

 perhaps many, families; the MagnoBaceae and the Nymphaeaceae are 

 excellent examples, for they show many stages in the change. The 



