The Scottish Naturalist. 267 



each consisting of a one-seeded ovary enclosed in two pairs of 

 enlarged fleshy sepals. In figs there is what reminds us of a 

 rose in its structure, but in the fig the hollow flower-stalk sup- 

 ports and envelopes a multitude of minute flowers, each one of 

 which has a small one-seeded ovary, — the so-called seed of the 

 fig. The flower-stalk is the eatable part, and makes up the great 

 mass of the fruit. 



In a few plants the bracts become fleshy, but this is rarely 

 the case, and I am not aware of any example of this structure 

 among Scottish species. The pine-apple (Auanassa sativa) shows 

 it well, and its appearance is probably familiar to most persons 

 nowadays. 



Elastic dehiscence of fruits frequently occurs in certain orders 

 of plants, notably among the Leguminosoz and Gcraniacece. The 

 mode of dehiscence of the former forces itself on one's notice, 

 to the ear at least, in the fine sunny days of autumn on any 

 piece of ground overgrown with broom or whins. The sharp 

 report of the bursting pods are often to be heard on all sides in 

 such circumstances. When the seeds are ripe in the fruits of 

 this order, there are two lines from tip to base of the pod — viz., 

 its two edges — where the structure renders them most liable to 

 give way. In dry sunny weather some moisture evaporates, and 

 contraction of the walls of the pod follows. If this goes beyond 

 a certain limit, it becomes too great for the resistance offered 

 at these lines, which suddenly give way, the two halves burst 

 apart, and the jerk throws out the seeds, often to a distance ot 

 several inches, or even feet. In the wild geraniums each carpel 

 usually contains only one seed, but generally five carpels are 

 present in each flower. The ovaries are closely adherent in the 

 flower to the base of a central column, while their long styles 

 are adherent to the column nearly to their tips. When the seed 

 is ripe, in dry weather, each ovary separates suddenly from its 

 attachment, while the style remains adherent to the column, and 

 thus throws the seed, as if from a sling, to some distance. In 

 the nearly-allied wood- sorrel (Oxalis) the seed is thrown out by 

 a different mechanism. The fruit is a capsule that, when the 

 seed is ripe, bursts into five parts in which the seeds lie. Each 

 seed has on outer coat or arillus in addition to the usual coats, 

 and this arillus is very elastic. When the fruit bursts the fleshy 

 arillus contracts through loss of moisture, bursts, and by its 

 elasticity propels the seed, as one propels a pea from between 

 the finger and thumb. Still another mode of elastic dehiscence 



