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On the Floral Development op Helianthus annuus. 



By W. H. Gilburt. 

 {Read October 25, 1878.) 

 PLATE IX. 



In the " Journal of Botany " for February of this present year 

 there is a paper by Dr. Maxwell T. Masters, entitled " Side-lights 

 on the Structure of Composites," in which, after describing a pro- 

 liferous and in other respects abnormal specimen of Helenium 

 autumnale, he raises the question as to whether the Composite 

 possess a true calyx or not. In order to find an answer more or less 

 satisfactory, observations were made, the results of which I now pro- 

 pose to lay before you. Not that the examination of one species in an 

 order containing 10,000 or more can in any sense be conclusive, but 

 it may furnish a standard of comparison, and a point of departure. 



You will all doubtless be aware that the theory now held with 

 regard to the various organs which go to make up a flower, is " that 

 the calyx, corolla, stamens, and pistils are, notwithstanding their 

 varied forms and functions, only modifications of one another, and 

 all are, again, only modified leaves." 



However improbable this theory may at first sight appear, an 

 acquaintance with the developmental history or morphology of the 

 flower, and the fact that each and all are found reverting to the 

 original type, will show that no other hypothesis yet advanced can 

 be considered tenable. 



The order of development of leaves in all plants is strictly acro- 

 petal, and consequently, regarding the various parts of the flower as 

 modified leaves, they should be developed in the same order ; the 

 lowest or outermost first, the others following in regular sequence. 

 This law holds good in most, if not in all orders but the Composite, 

 and here, from some cause, it is disturbed, and the calyx does not 

 appear till late, if at all. 



In the species now under consideration, if a section be made of a 

 very young capitulum, which is always found at the summit of 

 either a primary or secondary stem, it will be seen that the apex of 

 the stem has become depressed and extended in diameter, having 



