Source: G. E. Klemming, ed., Piae Cantiones. S. Trinitas. Iesus Christus. S. Spiritus. S Maria. (1886), p. 11.

De radice processerat
Iesse virga mirifica.
Huius virgae mysterium
si sane vis percipere,
virginis puerperium
tu debes intelligere,
quae mirum florem gesserat
faecunda vi deifica.
Flos Christus est in seculo,
dans odorem suauiter
et in coeli rosario
coruscans aeternaliter.
In fructum flos conuertitur
Gustando salutiferum:
Hoc est corpus meum, dum
loquitur natus ante Luciferum.
Granum, de cuius fructibus
egens turba reficitur,
Christus pro nobis omnibus
cadens in terra moritur.
Flos Christos est in seculo, etc.

Note from Klemming:

"P. C. 3." This refers to Piae Cantiones (1582), p. 3.

See also: Guido Maria Dreves and Clemens Blume, eds., Analecta Hymnica Medii Aevi, Vol. 45b. Cantiones et Motetten des Mittelalters. (Leipzig: O. R. Reisland, 1904), pp. 135-6, #168.

Other sources of Latin hymns found in Piae Cantiones:

• Guido Maria Dreves and Clemens Blume, eds., Analecta Hymnica Medii Aevi, Vol. 1.  Cantiones Bohemicae. (Leipzig: O. R. Reisland, 1886).

• G. E. Klemming, ed., Piae Cantiones. S. Trinitas. Iesus Christus. S. Spiritus. S Maria. (1886). Primary source for many scholars, including Dreves, Woodward and others.

• George Ratcliffe Woodward, Piae Cantiones: A Collection of Church & School Song, chiefly Ancient Swedish, originally published in A.D. 1582 by Theodoric Petri of Hyland. (London: Chiswick Press for the Plainsong & Medieval Music Society, 1910).

• Sheet music for some hymns can be found in George Ratcliffe Woodward, The Cowley Carol Book, First & Second Series. Table Of Contents. (London: A. R. Mowbray & Co., Ltd., ca. 1902, 1912).

• Translations of some carols can be found in John Mason Neale and Thomas Helmore, eds., Carols for Christmas-tide (London: Novello, 1853). By the same authors was Carols for Easter-tide (1854).

• Translations and sheet music for some hymns can be found in Charles L. Hutchins, ed., Carols Old and Carols New (Boston: Parish Choir, 1916).

• Scans of individual pages from Piæ Cantiones (in the Adobe PDF format) can be downloaded from Facsimiles Piae Cantiones (http://www.spielleut.de/facs_piae_cantiones.htm; accessed June 15, 2009).