Poinciana 

 regia. 



Erythrina 



corallo- 

 dendron. 



360 STUDIES IN SEEDS AND FRUITS 



but here the structural characters of the fruit act as final checks. 

 In short broad pods like those of Ulex there is no constriction 

 as a result of the failure of the ovules. The same remark 

 applies to those of Picia ; but here the absence of any contrac- 

 tion of the legume is due chiefly to the failures occurring 

 usually at the ends of the fruit. When several ovules and 

 young seeds fail at the ends of a legume, we have tapering 

 extremities. Such failures do not necessarily lead to shorten- 

 ing of a legume. An unusually short fruit is associated with 

 an unusually small number of ovules in the flower. 



Length in a legume is one of the pre-disposing causes ; 

 and in such a case even a dense ligneous texture, as in Poinciana 

 regia^ may not be sufficient to suppress the tendency. Here 

 the failure of seeds that have advanced in their growth seems 

 to have but little influence ; but if a few contiguous ovules 

 abort soon after fertilisation, or if a few contiguous seeds fail 

 in a very early stage, a slight constriction of the pod is produced, 

 the place of the seeds being occupied by ligneous material. 

 Thus in a legume of Poinciana regia^ where the space of four 

 seeds was thus filled up, the width of the legume was reduced 

 from 48 to 40 millimetres. 



Coming to the typical moniliform legumes, I will begin with 

 those of Erythrina corallodendron^ which first led me to undertake 

 this inquiry. Here there is a distinct relation between the 

 beading of the pod and the failure of very young seeds ; but 

 this is not the whole of the matter, since the narrowest con- 

 strictions show no trace either of ovule or of seed. Here it 

 may be that we have an indication of the influence of rudi- 

 ments of ovules in the flower which disappear altogether in the 

 fruit. In the accompanying diagram I have represented a 

 typical seven-seeded dry pod about 115 millimetres long. At 

 A, E, and F the constrictions are very narrow, 2 millimetres or 

 less, and there is no trace of either seed or ovule. The other 

 constrictions (B, C, D) are broader (2*5 millimetres to 3 milli- 

 metres), and here aborted seeds 11*5 millimetres long occur, the 

 length of the constricted portion being regulated by the number 



