322 



KNOWLEDGE & SCIENTIFIC NEWS. 



[January, 1906. 



all is the oroiip of carpels which £jo to make up the 

 pistil. For the present purpose it will be all sufticient 

 to think of the flower as consistini; of these four parts— 

 calvx, corolla, stamens, and pistil. As well, in not a 

 few flowers, there are present a number of appendages 

 to wliirh has been sjiven the name bracts. 



MOON DAISIES.- It is interesting to note the manner in whicli tlie 

 leaves become more like tlie bracts as they approach the flower. 



As has Ijeen stated, the calyx of the flower is some- 

 times green and sometimes coloured. This is equiva- 

 lent to saying that the sepals on occasion produce 

 chlorophyll, and in this condition they, of course, carry 

 on the functions of an ordinary leaf. This being so it 

 is interesting to see whether it is possible to discover 

 any relation between the sepal and the leaf other 

 than the fact that both indicate the presence of chloro- 

 phvll. In this connection the case of the ordinary 

 herbaceous Pa^ony is very noteworthy. If a number of 

 specimens of this flower be examined it will be found 

 that quite often the sepals of the calyx are really modi- 

 fied leaves. Indeed, time and again it is impossible to 

 determine definitely the exact nature of the organs, and 

 the confusion is all the greater when, as is often the 

 ca.se, a large area of the leaf-like sepal is as gaily 

 coloured as a petal. 



The common Moon Daisy of the meadows {Chrysan- 

 themum lauanthcmuni) re\eals in the nature of its growth 

 the whole course of the evolution of the green bracts 

 which encircle the mass of ray florets. Gather one 

 of the long-stemmed blossoms, taking care to pluck it 

 with as many of the lower leaves attached as possible. 

 Now, starting from the bottom of the stem where there 

 is nothing but the typical well-developed leaves of the 

 species, allow the eye to travel upwards towards the 

 flower head. With every fresh stage in the approach 

 to the top there is a notable decrease in the size of the 

 leaves. Finally they lose their distinctive form alto- 

 gether, until just below the flower the leaflets drift into 



simple lobes, which bear a striking resemblance to the 

 green bracts which form such an important part of the 

 flower head. 



XLuncrous instances might be noticed in which it 

 would be clearly .seen that we shall not be far wrong in 

 assuming that the green sepals of the calyx arc really 

 nothing more than advanced leaves. But these sepals 

 are often as g.iily coloured as the petals them.sclvcs, 

 bring entirclv devoid of the green tissue which is present 

 in the leaf. In certain sp<"cies, such a.s the Campanulas, 

 the sepals and petals are actually joined together to 

 form one big bell-shaped corolla. Under these circum- 

 stances it may not be amiss to consider for the time 

 being both the floral appendages, whether sepals or 

 petals, as one and the same thing. 



The common garden Tulip is a well-known examolc 

 of a flower in which the petals and sepals arc identical ; 

 at any rate, as far as the ordinary obser\er cm say. 

 Now if we observe a large number of cultivated Tulip 

 blossoms we shall certainly find that in not a few some 

 of the sepals — that is to say, the outside circle of ap- 

 pendages — are partly or wholly g-reen, proving' beyond a 

 shadow of a doubt whence they have their origin. This 

 is especially so in the case of double Tulips, and the 

 reason for this is probably owing to the fact that the 

 double flower is a more artificial form of Tulip than is 

 the single variety. It is well known that the more 

 highly cultivated and artificially specialised is a plant 

 the greater is the tendency to variation and reversion to 

 earlv tvpes. Moreover, in the Tulip, just below the 



TtLIPS. -In double 



varieties of this (lower the leaf origin of the 

 is very apparent. 



flower a strange leaf-like appendage is often produced, 

 and the intelligent observer will readily see in this a 

 kind of half-way hou.se between the leaf and the .sepal. 



Perhaps a .still more striking proof of the leaf origin 

 of both petals and sepals is to be seen in the flower of 

 the Summer Sno\\flake [Leucojum cesiiviim). Each 



