954 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



In conclusion, I may draw attention to the fact that these abnormal 

 flowers of Helenium are not "sports" or "monstrosities" in the rigid sense 

 of the word. For they display no structural development which is in any 

 way foreign to, or subversive of, the ordinary laws of vegetable growth. 

 They are " sports " or " freaks " only in the sense that the various parts of 

 the inflorescence which, in the normal condition of the genus and order, 

 are, for special purposes connected with the reproduction of the plant, 

 specially modified in the direction of, as it were, a contraction and sup- 

 pression of their vegetative growth, become, under the stimulation of the 

 tiny Phytoptus (the exact rationale of which we do not yet understand), 

 induced or forced to assume an extreme expansion of growth and a 

 vegetative development like that of the more actively growing parts of the 

 plant. But it should ever be remembered that all these changes, whether 

 caused by parasitic stimulation or other agencies, are always governed by 

 the ordinary definite laws of vegetable growth, and represent what is 

 merely a further extension in development of parts already present. 

 No new organs appear, but only the same old organs under a modified 

 (in the direction merely of luxuriant vegetative expansion) form. 



But I go further than this, and maintain that these abnormal develop- 

 ments, especially when gradual transitional stages occur between the 

 perfectly normal and the extreme abnormal form, throw great light on the 

 exact morphology of the different organs affected, and this I have already 

 drawn attention to in the foregoing pages. For example, from these 

 virescences, we should learn, even if we never knew it before, that the 

 ovary consists of two carpellary leaves ; that the stamens and carpels 

 are foliar organs borne at all times on an axis (the various proliferations 

 being but upward extensions of the normally suppressed axes of the 

 florets) ; and that the corollas of the two kinds of florets are homologous 

 structures, both modified to subserve their highly adaptative functions. 



A quite interesting point, as illustrating what I hold to be the true 

 views of Nageli, Drude, Grant Allen, Celakovsky, and others, as to the 

 origin of the petals from the stamens, is the fact that in some of the 

 virescent forms of the ray-florets the yellowish foliaceous stamens are 

 hardly distinguishable from the narrow, separated segments of the 

 ligulate corolla, as is well seen in fig. 210, o. 



From these cases we further learn that the pappus (an adaptation to 

 subserve fruit- and seed-dispersal) is merely a highly modified calyx, 

 whose segments have not only become hair-like in texture and colourless, 

 but also subdivided into a greater number of members than the usual 

 five. If the pappus is not the homologue of the calyx, where are we to 

 look for the latter in the normal floret ? for it cannot be supposed to be 

 entirely absent ! In view of the fact that in the virescent florets there is 

 very frequently present below the corolla a whorl of small, green, linear 

 leaves, the conclusion inevitably must be that this whorl is the calyx 

 appearing in its natural position, while the pappus in these cases is absent 

 as such. The idea that the two are homologous is further strengthened 

 by the fact that, in cases where these little green leaves are incomplete in 

 number, minute subulate or hair-like structures occur either amongst or 

 close above or below them ; these are probably remnants of the normal 

 pappus- formation. 



