Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.

Studies in the Anatomy and Morphology of the Composite Flower II. The Corollas of the Heliantheae and Mutisieae

Minna Frotscher Koch
American Journal of Botany
Vol. 17, No. 10 (Dec., 1930), pp. 995-1010
Stable URL: http://www.jstor.org/stable/2435758
Page Count: 18
  • Read Online (Free)
  • Download ($12.00)
  • Subscribe ($19.50)
  • Cite this Item
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Studies in the Anatomy and Morphology of the Composite Flower II. The Corollas of the Heliantheae and Mutisieae
Preview not available

Abstract

1. The ray "corolla" of the Heliantheae constitutes a structure which consists of a typical composite corolla plus two or three appressed calyx bundles. The calyx and corolla have apparently become fused, and the vascular supply of these floral whorls united in part. The median bundles of the calyx and the lateral bundles of the corolla are fused and are no longer distinct. In the Heliantheae it is believed that three of the median bundles of the calyx are retained as separate strands and are fused to the under surface of the ray corolla as the distinctly prominent, large bundles. These bundles are surrounded by loose parenchymatous tissue that is distinct from the tissue of the corolla. 2. Bidens cernua is used as an example in the Heliantheae to show the presence of these appressed bundles on the dorsal surface of the ray corolla. At the base of the ray floret innumerable discrete vascular strands are given off from a bundle in the receptacle. Four large bundles persist (a, b, c, and d). At the top of the achene the four bundles separate to form the corolla supply. The two prominent, large appressed bundles are derived from a and b, and c is the prominent bundle that lies between a and b in the corolla. Bundles a, b, and d form the typical venation of the corolla. The split in the corolla comes at a point in a radius that lies over an aborted bundle. 3. Four strands given off from the floral stele in the base of the disk floret of Bidens cernua furnish the vascular supply of the floret. At the top of the achene one of the four bundles separates into two bundles, thus increasing to five fused lateral bundles the supply that leads into the corolla. This number of fused lateral bundles is always to be found in the disk corolla. The stamen and stylar bundles are adnate to the corolla bundles. 4. A diagrammatic scheme which represents the writer's conception of the phylogenetic development of the ray floret is given. It is believed that the vascular system of the calyx is responsible for the elaborate, heavy veined "corollas" in the Heliantheae. 5. In the ray floret of Rudbeckia triloba vestiges of stamens were found. Such a finding emphasizes the relationship that exists between the ray and disk corollas. 6. There are no appressed bundles on the under surface of the ray corolla of Helenium autumnale. At the base of the achene of the ray floret there are two bundles. These bundles separate into five bundles and persist through the wall of the ovary, leading into the corolla. One of the bundles aborts, and in a radius in the corolla which lies above the lost bundle the split in the corolla occurs. The anatomy of the disk corolla is similar to the one described for Bidens cernua. 7. The morphology of Grindelia squarrosa is characteristic of the Heliantheae. There are no resemblances with forms such as Aster and Solidago which belong in the same tribe as Grindelia. 8. The Mutisieae have three kinds of florets: ray, tubular, and bilabiate. The venation of the ray corolla is similar to that of the "Aster" type. The tubular corolla is typical of the venation of the "Discoid" type. The bilabiate floret is similar to the disk floret at the base of the floret, but in the tube of the corolla the members of three fused lateral bundles separate at the three sinuses to supply a strap-shaped lobe and two shorter lips. 9. The bilabiate corolla of the Mutisieae is believed not to be the inter-mediate form from which the ray corolla has been derived, as indicated by: 1, the tip-lobing of the ray corolla not being limited to three lobes; 2, division of the lobes of the corolla of Centaurea; 3, variation of the corollas of the Mutisieae; 4, vascular anatomy of the ray corolla. 10. No anatomical evidence could be found to show any relationship or connection of the Compositae with any other family usually considered closely related. The closest resemblance to a composite type was found in the Calyceraceae; yet the anatomy of Boopis anthemoides, a member of this group, shows only those similarities that are common to gamopetalous corollas in which vascular reduction is taking place.

Page Thumbnails

  • Thumbnail: Page 
995
    995
  • Thumbnail: Page 
996
    996
  • Thumbnail: Page 
997
    997
  • Thumbnail: Page 
998
    998
  • Thumbnail: Page 
999
    999
  • Thumbnail: Page 
1000
    1000
  • Thumbnail: Page 
1001
    1001
  • Thumbnail: Page 
1002
    1002
  • Thumbnail: Page 
1003
    1003
  • Thumbnail: Page 
1004
    1004
  • Thumbnail: Page 
1005
    1005
  • Thumbnail: Page 
1006
    1006
  • Thumbnail: Page 
1007
    1007
  • Thumbnail: Page 
1008
    1008
  • Thumbnail: Page 
1009
    1009
  • Thumbnail: Page 
1010
    1010
  • Thumbnail: Page 
[unnumbered]
    [unnumbered]
  • Thumbnail: Page 
[unnumbered]
    [unnumbered]