It has taken me some time to study the Lesser Stemma more closely. One of the critical questions in the course of this analysis was where its editor had obtained his textual commentary from. The final page, 8v, contains the familiar Great Stemma statement:
Sicut Lucas evangelista per Nathan ad Mariam originem ducit, ita et Matheus ev(an)glista per Salomonem ad Ioseph originem demonstrat. Id est de tribu Iuda, ut appareat eos de una tribu exire, et sic ad Christum secundum carnem pervenire. Ut compleatur quod scriptum est: "Ecce vicit leo de tribu Iuda radix David," leo ex Salomone, radix ex Nathan.But in a radical reversal of meaning, the Lesser Stemma bolts on to this a core statement from Julius Africanus. The following is my transcription of this from the Burgos Bible (the layout of the pages is tabulated on my website):
Ut clarius fiat, quod dicitur: ipsarum generationum consequentias enarravimus.
A David generatio per Salomonem, quam dinumerat Matheus, tercium a fine facit Mathan, qui dicitur genuisse Iacob patrem Ioseph. Per Nathan vero Lucas generationum ordinem texens, tercium nichilominus eiusdem loci facit Melchi. Nobis imminet ostendere, quomodo Ioseph dicitur secundum Matheum quidem patrem habuisse Iacob, qui inducitur per Salomone: secundum Lucham vero Heli qui ducitur per Nathan, atque ipsi, id est Heli et Iacob, qui erant duo fratres, habentes alius quidem Mathan, alius quidem Melchi patres ex diverso genere venientes, etiam ipsi Ioseph avi esse videantur.
Est ergo modus Mathan et Melchi de una eadem que uxore Hesta nomine diversis temporibus singulos filios procrearunt, quia Mathan, qui per Salomonem descendit, uxorem eam primus acceperat et relicto uno filio Iacob nomine defunctus est. Post cuius obitum, Me[l]chi qui Nathan genus ducit. cum esset ex eadem tribu, ex eadem tribu[sic], relictam Mathan accepit uxorem ex qua et ipse suscepit filium nomine Heli per quod ex diverso patrum genere efficiuntur Iacob et Heli iterini fratres quorum alter, id est Iacob, fratris Heli sine liberis defuncti uxorem ex mandato legis accipiens genuit Ioseph natura quidem germinis suum filium, propter quod scribitur Iacob autem genuit Ioseph: secundum legis vero praeceptum Heli efficitur filius, cuius lacob qui erat filius Mathan uxorem ad suscitandum fratris semen acceperat et per hoc rata invenitur atque integra generatio et tan, quam Matheus enumerat, et tan, quam Lucas competenti [?]ione designat.
I soon found that the above Latin text comes from one of the early translations of the Letter to Aristides. This was produced in the early years of the 5th century (perhaps 402 or 403) by Rufinus of Aquileia (see Christophe Guignard, La Lettre de Julius Africanus à Aristide sur la Généalogie du Christ, 2011, p. 24 ff. for a discussion). With a good text of Rufinus (the passage is numbered 1.7.5-11), I was also able to unlock most of the manuscript abbreviations and correct my transcription at places where I had not initially been able to make out the script.
Here is George Salmon's translation of the same passage of Africanus, which has been put into first-person speech though this is not necessarily required by the Africanus text:
But in order that what I have said may be made evident, I shall explain the interchange of the generations. If we reckon the generations from David through Solomon, Matthan is found to be the third from the end, who begat Jacob the father of Joseph. But if, with Luke, we reckon them from Nathan the son of David, in like manner the third from the end is Melchi, whose son was Heli the father of Joseph. For Joseph was the son of Heli, the son of Melchi. As Joseph, therefore, is the object proposed to us, we have to show how it is that each is represented as his father, both Jacob as descending from Solomon, and Heli as descending from Nathan: first, how these two, Jacob and Heli, were brothers; and then also how the fathers of these, Matthan and Melchi, being of different families, are shown to be the grandfathers of Joseph. Well, then, Matthan and Melchi, having taken the same woman to wife in succession, begat children who were uterine brothers, as the law did not prevent a widow, whether such by divorce or by the death of her husband, from marrying another. By Estha, then—for such is her name according to tradition—Matthan first, the descendant of Solomon, begets Jacob; and on Matthan’s death, Melchi, who traces his descent back to Nathan, being of the same tribe but of another family, having married her, as has been already said, had a son Heli. Thus, then, we shall find Jacob and Heli uterine brothers, though of different families. And of these, the one Jacob having taken the wife of his brother Heli, who died childless, begat by her the third, Joseph—his son by nature and by account. Whence also it is written, “And Jacob begat Joseph.” But according to law he was the son of Heli, for Jacob his brother raised up seed to him. Wherefore also the genealogy deduced through him will not be made void, which the Evangelist Matthew in his enumeration gives thus: “And Jacob begat Joseph.” But Luke, on the other hand, says, “Who was the son, as was supposed (for this, too, he adds), of Joseph ..."The Letter to Aristides was transported to the West as part of Rufinus's Latin translation of the Ecclesiastical History of Eusebius of Caesarea. Plainly this explanation of the gospel contradiction was popular and formerly in wide circulation. Mommsen discovered 90 extant manuscripts of this work of Rufinus in the late 19th century, according to Dr Guignard.
If the passage was already in current use in the 5th century, it would not be surprising that a partisan should have taken it up and used it to modify the Great Stemma to bring it into harmony with the contentions of Africanus, Eusebius and Rufinus, and at the same time to repel the Joachim theory, which is based on an apocryphal text, the Protevangelium of James.
The Lesser Stemma is however not completely faithful to Africanus, who omits two names (Matthat and Levi) between Joseph's father Heli and the more senior Melchi. At least as present in the Burgos Bible, the Lesser Stemma restores these names, but it does so in a non-orthodox order: it muddles the order of Melchi-Levi-Matthat and presents this as Levi-Macham-Melchi.
The greatest oddity of this text is that it contradicts the drawing alongside it. In the Burgos Bible, both genealogies clearly terminate at Joseph. In the image at right, the upper roundel (Joseph filius Iacob qui desponsavit Mariam) is the terminus of the Matthaean genealogy, and the lower roundel (Joseph sponsus Marie de qua natus est Christus) is the terminus of the Lucan genealogy. Yet the text retains the notion from the Great Stemma that the Lucan genealogy should end at Mary. This is an odd situation; I cannot at present see any coherent explanation for it.