MARCH. 69 



are some of the prime factors which have fashioned the 

 world of living things which we see to-day, and these 

 forces are still at work continually around us. 



The adaptations whereby plants secure the most favour- 

 able conditions for the seeds which they produce are so 

 abundant and so easily studied that we may well devote 

 a little attention to them at this season of the year. I have 

 referred to them in last month's notes, but only to a slight 

 extent. 



In the course of our walks through the Town Belt or 

 along the suburban roads we must have heard, on the few 

 bright days we have enjoyed this autumn, the pods of the 

 broom and the whin cracking sharply, and if we have had 

 the patience to stand for a minute to watch and listen, we 

 would have probably noticed that the seeds were thrown 

 out to a distance of several feet. As the pods come to 

 maturity their inner lining becomes tense and elastic, so 

 that when the sun shines strongly on them and the air is 

 dry, the pressure exerted is such as to burst the walls and 

 throw out the seeds. It would not be of much advantage 

 to a broom bush were its seeds to drop straight down from 

 the branches ; the new seedlings would at once enter into 

 competition with the parent plant and they would starve 

 each other. But by sending its progeny some little 

 distance into the world the young plants enter into com- 

 petition with other organisms and the chances of increase 

 of the future generations of brooms are thus greatly 

 increased. Mechanical devices like this are not very 

 numerous, but that they are very effective is shown by 

 the way in which both whin and broom succeed in spread- 

 ing and in holding their own against all comers. 



There is a common kind of balsam grown in many 

 gardens in town a reddish or purplish-green plant stand- 

 ing some three feet or so in height and bearing peculiarly 

 pouched white or pink flowers. Its seed-pods, which look 

 like elongated buds, are very curious. If you take hold of 

 them between the finger and thumb when they are ripe 

 they immediately squirm in a most remarkable manner. 

 I have seen a lady drop one under the impression that it 



