12 BURSA BURSA-PASTORIS AND BURSA HEEGERI : 



day before the buds open. As the buds are at that time quite small, the 

 technique of cross -pollination is somewhat delicate'. However, with a 

 needle-pointed forceps the calyx, corolla, and stamens may be readily cut 

 away from about the young- pistil, and the eye and hand soon become so 

 skilled that the work can be done swiftly and with as much accuracy as 

 may be attained in the castration of a lily. 



PURE CULTURES OF BURSA BURSA-PASTORIS. 



The four biotypes of Bursa bursa-pastoris with which this paper mainly 

 deals are distinguished from each other by certain characteristic lobingrs of 

 the leaves. For convenience I have assigned to them the names Bursa 

 bursa-pastoris heteris, B. bp. tenuis, B. bp. rkomboidea, and B. bp. simplex. 

 It has been impossible to determine which of Almquist's "elementary 

 species" agree with these, but it is almost certain that he has assigned 

 names to several fluctuations of the same biotype. If this is true my four 

 types are more inclusive than his and under my names will need to be 

 grouped a number of forms which he has considered distinct elementary 

 species. 



Bursa bursa-pastoris heteris n. sp. element. 



Plants belonging to this biotype have the leaves divided to the midrib, 

 the terminal lobe being usually separated from the nearest lateral lobes by 

 deep, clean-cut incisions. The lateral lobes consist essentially of two fea- 

 tures — an elongated, attenuate portion which I call the ' 'primary lobe, ' ' and 

 a more or less rounded or angtilar portion which forms a ' ' secondary lobe ' ' 

 in the distal axil of the primary lobe (fig. 2). As in the characterizations 

 of all the following forms, this description refers to the climax-leaves of the 

 rosettes in properly grown specimens, since the juvenile leaves of all the 

 elementary species of Bursa are entirely unlobed, and starved or crowded 

 specimens of all the forms may reach maturity with only juvenile leaves, 

 as already stated. Several of Almquist's recently described forms would 

 obviously range themselves itnder this description, though it is always pos- 

 sible, of course, that forms which possess the described characteristics may 

 have still other permanent characteristics which would render them distinct 

 elementary species. 



The first of the forms recognized by Almquist which can certainly be 

 placed here is his Capsella bp. rubella (see his figs. 5 and 6). His C. bp. 

 angustiloba (his figs. 56 and 57) represents the most pronounced develop- 

 ment of this type, and others which probably belong here are reuteri (fig. 

 11), grandiflora (figs. 12 and 13), hiemalis (fig. 20), grossa (fig. 22), au- 

 tumnalis (fig. 24), segetum (fig. 28), wittrockii (fig. 44), rhombea (fig. 48), 

 rhombella (fig. 53), ellipsoidea (fig. 55), a.ndifucorum (fig. 60). 



My first pure-bred family of B. bp. heteris (pedigree-number 040.3) was 

 grown from seeds collected by J. Marion Shull at Edgewood, New Carlisle, 



