256 SCIENCE PROGRESS 



type-leaf. The well-known German botanist Goebel 1 regards 

 the foliage-leaf as the type of which all other kinds of leaf are 

 modifications. The fact that a "flower" is, after all, only a 

 highly modified leafy shoot is shown by the frequent occurrence 

 in our gardens and in Nature of those peculiar " sports " known 

 as "floral proliferations," in which the usually shortened axis 

 of the flower elongates, under the influence of certain factors, 

 as, e.g., excess of nourishment in the soil, into a leafy shoot, 

 while the floral leaves become, in part or wholly, changed in 

 texture, colour, and size, so as to resemble ordinary foliage- 

 leaves, frequently producing at the same time branches in their 

 axils. Roses not rarely exhibit this " freak." 



The above considerations enable us to see of what other 

 parts of the plant the flower is the natural equivalent. The 

 central conical disc or receptacle is after all merely a highly 

 contracted or shortened shoot on and around which the various 

 foliar organs of the flower are seated. It is probable that, as 

 Goebel believes, each type of floral leaf, whether sepal, petal, 

 stamen, or carpel, has been derived by modification of form 

 and function, and reduction in size, of green foliage-leaves. 

 We shall see more clearly how this came about further on. 



In the meantime we may note that it is almost certain that 

 the flowers of the most primitive Angiosperms did not possess 

 a double perianth (calyx and corolla) such as we see to-day 

 in the Lily and Buttercup. Many of our present wind- 

 fertilised flowers, such as the Poplar, Oak, etc., have either no 

 perianth at all or a single, colourless, ill-formed one. How 

 far this condition is a case of reduction from much better- 

 furnished types we hardly are able to estimate. The consensus 

 of opinion to-day seems to point to the fact that the petals, at 

 any rate, are a comparatively recent formation within the flower. 

 It was Grant Allen 2 who first pointed out that petals are in all 

 cases derived by modification of pre-existing stamens. Nageli 3 

 and then Drude 4 also maintained this position. Celakovsky, 5 in 



1 "Die vergleichende Entwickelungsgeschichte der Pflanzenorgane " (Schenk's 

 Ha?idbuch der Botanik, vol. iii. part i. p. ioo, 1884). 

 ' The Colours of Flowers, 1882. 



3 Mechanisch-physiologische Theorie der Abstammu?igslehre, p. 496, 1884. 



4 "Die systematische und geographische Anordnung der Phanerogamen " 

 (Schenk's Handbuch, vol. iii. part ii. 1887). 



5 " Ueber den phylogenetischen Entwickelungsgang der Bliithe," etc., part i. 

 p. 7 {Kgl. bohm. Gesellsch. d. Wzssensch., Prag, 1900). 



