3i6 



STUDIES IN SEEDS AND FRUITS 



handling and actual inspection can be more effectual than the 

 data in this table in bringing out the fact that the growth of 

 the fruit-case is for a long time far in advance of that of the 

 seed. As typical of the behaviour of legumes I will take 

 the pods of the Scarlet-runner (Phaseolus multiflorus) and the 

 Broad Bean {Faba vulgaris)^ and as representing the capsules 

 the fruit of Iris Pseudacorus. 



In the young pods of the Scarlet-runner and of the Broad 

 Bean, when less than half the mature size, the contrast between 

 the large fruit-case and the diminutive, partially formed seeds 

 is very striking. On the average the weight of the fruit-case 

 would be about 90 per cent, of the total weight of the entire 

 fruit. When the pods have attained maturity in the moist 

 condition, the proportion is lowered to 50 or 60 per cent. ; 

 and in the air -dried pods it is still further reduced to 25 

 or 35 per cent. From an early stage in the fruit's develop- 

 ment until it hangs as a dried-up pod on the plant there is 

 a continual decrease in the proportional weight of the pericarp 

 or fruit-case. Up to the time of maturity this decrease is 

 due to the active growth of the seeds. After maturity it 

 arises from the larger water- contents and the consequently 

 greater drying capacity of the fruit-case. 



The capsules of Iris Pseudacorus give similar indications. 

 Here also we notice in the columns of the table that there 

 is a continuous decrease in the relative weight of .the pericarp. 

 When the young fruit is only two-fifths of the mature size, 

 the proportion is as much as 77 per cent. ; and it attains the 

 minimum of 25 per cent, in the completely air-dried fruit. 

 If we had commenced with a still younger fruit, the proportion 

 of pericarp would have been as much as 85 or 90 per cent. 

 But it is obvious that this continuous decrease is brought 

 about by different causes during the growing and the drying 

 stages. In the early growing stage, when the seeds are small 

 and their contents more or less unformed, the pericarp greatly 

 predominates ; but as growth proceeds and the ripening stage 

 is approached, the seeds rapidly add to their weight, and the 



