HOW PLANTS LIVE AND WORK. 327 



slightly sticky from a sugary solution which forms upon it. There 

 still remains the part of the pistil which corresponds to the body 

 of the bottle. This is called the ovary, because in it are formed 

 the ovules or young seeds. 



The ovary of the Wallflower is divided into two chambers by 

 a vertical partition, and each chamber contains two rows of ovules 

 running down its length. The structure of the stamens and pistil 

 may seem a little complicated at first, but, in view of the profound 

 interest of the process next to be described, it is well worth while 

 to take a little trouble to master their main features. 



We have, then, on the apex of the flower-stalk — after removing 

 sepals and petals — six stamens, each with its terminal pollen-box, 

 and a single central pistil consisting of stigma, style, and a basal 

 ovary or ovule-box. In order that fertilisation may be effected, 

 and a new plant formed, the contents of a pollen grain must come 

 m contact with the contents of an ovule, and all the details of the 

 flower's structure are arranged to secure the fusion of the two. 

 The delicious scent and brilliant colouring of the petals, and the 

 honey inside the sepals, are formed solely with this object in view. 

 A necessary preliminary to fertilisation is that the pollen shall 

 gain access to the stigma of the pistil. It can easily be proved by 

 an interesting experiment that, unless this takes place, the ovules 

 will never become seeds capable of growing into new plants. To 

 show this, it is only necessary to remove the stamens from a flower 

 before their pollen has had any chance of reaching the stigma. As 

 the anthers of the stamens burst as soon as the flower opens, the 

 flower must be opened artificially in order to remove the stamens 

 in time. With a little care the operation may be performed so as 

 not to otherwise injure the flower. If now the plant be covered 

 by gauze to preclude the possibility of pollen being brought by 

 insects, it will be found that the flower will wither without forming 

 ripe seeds. That this effect is entirely due to the absence of 

 pollen may easily be shown by transferring a little pollen (by 

 means of a fine brush) from another flower to the stigma of the 

 one under experiment. If this be done, the seeds will ripen in a 

 perfectly healthy and normal manner. 



It is quite clear, therefore, that the problem each flower has to 

 solve is — to contrive a means by which the stigma of its pistil 



