A series of field trials were performed in order to compare the yield stability of plants of the independent vascular supply (IVS) type peduncle vascular architecture with those of the more usual branched type. The IVS plants gave a low stable, source-limited yield; the plants attained maturity four weeks earlier than those of Maris Bead. The source-sink relationships of the genotypes investigated were established. The potential values of IVS type plants as commercial varieties are discussed. Studies of the growth and development revealed a difference in pod wall structure and the distribution of stomata and pod hairs: this could be related to pod drying. The growth of all parts of the raceme was studied by plotting fresh and dry weight changes, a sequence of development of tissues was established, the peduncle growing first, then the pedicel, then the pod and finally the seed. Genotypic differences in growth rate were observed. These findings were related to the accompanying vascular development within the raceme. The source of the assimilates rapidly translocated into the seeds during early, rapid growth was established. The results obtained are discussed and an ideotype constructed on the basis of the information obtained.