666 THE POPULAR SCIENCE MONTHLY. 



is still more marked in that the number of ovaries is reduced to six, 

 that is to say, two whorls of three each, accompanied by nine stamens, 

 similarly divisible into three rows. In all these very early forms (as 

 in their analogues the buttercups) the main point to notice is this, that 

 there is as yet no regular definiteness in the numerical relations of the 

 parts. They tend to run, it is true, in rows of three ; but often these 

 rows are so numerous and so confused that nature loses count, so to 

 speak, and it is only in their higher and more developed members that 

 we begin to arrive at any distinct symmetry, such as that of the flow- 

 ering rush. Even here, the symmetry is far from being so perfect as 

 in the later lilies. There are, however, a few very special members of 

 the alisma family in which the approach to the true lilies is even 

 greater. These are well represented in England by our own common 

 arrowgrasses inconspicuous little green flowers, with three calyx- 

 pieces, three petals, six stamens, and either six or three ovaries. Here, 

 too, the ovaries are at first united into a single pistil (as it is technic- 

 ally called), though they afterward separate as they ripen into three 

 or six distinct little capsules. One of our British kinds, the marsh 

 arrowgrass, has almost reached the lily stage of development ; for it 

 has three calyx-pieces, three petals, six stamens, and three ovaries, ex- 

 actly like the true lilies ; but it falls short of their full type in the 

 fact that its pistil divides when ripe into separate capsules, whereas 

 the pistil of the lilies always remains united to the very end ; and this 

 minute difference suffices, in the eyes of systematic botanists, to make 

 it an alisma rather than a lily. In reality, it ought to be regarded as 

 a benevolent neutral a surviving intermediate link between the two 

 larger classes. 



The specialization which makes the true lilies thus depends upon 

 two points. In the first place, all the parts are regularly symmetrical, 

 except that there are two rows of stamens to each one of the other 

 organs : the common formula being three calyx-pieces, three petals, 

 six stamens, and three ovaries. In the second place, the three ovaries 

 are completely combined together into a single three-celled pistil. 

 The advantage which the lilies thus gain is obvious enough. Then- 

 bright petals, usually larger and more attractive than those of the 

 alismas, allure a sufficient number of insects to enable them to dispense 

 with the numerous stamens and ovaries of their primitive ancestors. 

 Moreover, this diminution in number is accompanied by an increase in 

 effectiveness and specialization : for the lilies have only three sensi- 

 tive surfaces to their pistil, combined on a single stalk ; and the honey 

 is usually so placed at its base that the insect can not fail to brush off 

 pollen at every visit against all three surfaces at once. Again, while 

 the number of ovaries has been lessened, the number of seeds in each 

 has been generally increased, which also marks a step in advance, 

 since it allows many seeds to be impregnated by a single act of polli- 

 nation. Tbe result of all these improvements, carried further by 



