302 



CHAPTERS ON EVOLUTION. 



is not a single flower, but a collection of florets. A thistle (Fig. 

 203) or a daisy-head (Figs. 199 and 200), for example, is not one 

 flower, in the sense in which a buttercup or lily is single, but is an 

 aggregation of small stalkless flowers (200, co, co) closely packed 

 together on one main stalk. If we examine the thistle-head, we shall 

 find it to consist of numerous little flowers (203 c, c], of similar 

 appearance, each containing the essential organs and parts seen in 

 other single flowers. In the Centauries of our 

 waysides and cornfields, we witness the same 

 composite structure of the flower-head ; but 

 here, the outermost florets (202, a) of the 

 " head " have begun to develop into petal- 

 like organs, and have lost their stamens and 

 pistils. The Centaury, in other words, has de- 

 veloped the beginning of a low individuality ; 

 it is losing its completely compound nature, 

 and is advancing towards the singleness of 

 type of ordinary flowers. Thus, in Centaurea 

 nigra, these outer florets vary in size; they 

 may resemble the inner ones in size, or may 



^ . J \ / V- be larger, and they may want both stamens 

 J.W \ and pistils. In another species (C. scabiosa), 

 stamens and pistils never occur in the outer 

 florets ; and in Centaurea cyanus (Fig. 202) 

 likewise, these florets (a) are useless for repro- 

 duction, and are passing towards the type 

 and function of ordinary petals. So also in 

 the familiar dandelions (Fig. 201), we may 

 witness a stage in advance of the thistle. For 

 whilst the latter plant has its florets similar 

 and inconspicuous, the dandelion (Fig. 201) 

 has added to its similar florets the bright 

 corollas, which serve to render this wayside 

 plant so conspicuous to insect eyes as well as 

 to our own perception. When the dandelion 

 appears with its outer florets expanded, while 

 the inner florets have still to unfold, the flower 

 bears no inconsiderable resemblance to the 

 ordinary type of single flower. Far more 

 advanced, however, towards the individuality 



of other plants, are the marigolds, daisies (Figs. 199, 200), and their 

 allies. Here the likeness of the single flower deceives the non- 

 botanical observer into supposing that each daisy in reality cor- 

 responds to each buttercup or primrose in its constitution. For the 

 outer florets of the daisy and marigold have developed, as those of 



FIG. 201. DANDELION. 

 b, Ripe flower-head. 



