No. 568] X CAPSELLA BURSA-PASTORIS A BACHNOIDEA 225 



An examination of the herbarium material placed at 

 my disposal reveals the fact that plants, apparently 

 identical with C. orbicularis, occur in Europe. In the 

 Engelmann herbarium of the Missouri Botanical Garden 

 are two sheets (No. 3,661 and 3,664) containing specimens 

 which undoubtedly must be classed here. The latter sheet 

 bears the label: Thlaspi Bursa-pastoris humile. Heidel- 

 berg. April 1828. 



A culture of Capsella, derived from seed of a single 

 plant, unfortunately not preserved, escaped from culti- 

 vation in the Experiment Garden, and consisting of 182 

 individuals (Ehlers, No. 4,813), appears to be composed 

 entirely of orbicularis. And while I have never encoun 

 tered the plant in nature, these two facts lead us to another 

 possible explanation. Perhaps the appearance of orbic- 

 ularis in the original culture was due to an accidental 

 admixture, such as is almost impossible to guard against 

 when experimental plants are grown in a greenhouse used 

 for a variety of purposes. 



The exact relation which orbicularis bears to the other 

 types of Capsella here described can, of course, be de- 

 termined only after a series of experiments has been car- 

 ried out. However, the delay in the completion of the 

 manuscript, caused by the unfortunate destruction, by 

 fire, of the botanical laboratories of the University of 

 Michigan, enables me to add that a third generation of 

 orbicularis, the parent being No. 32,012Z?1P3, shows at 

 least two and possibly three types, of which one is espe- 

 cially interesting in having rather narrow leaves, at least 

 as compared with those of typical orbicularis. The con- 

 trast between the two forms is increased by the fact that 

 in the narrow-leaved form the foliage is entirely glabrous, 

 while in the typical orbicularis the leaves are covered 

 with numerous stiff, almost bristle-like, hairs. 



X Capsella Bursa-pastoris arachnoidea 

 By this name is designated the linear-leaved form, the 

 appearance of which induced us to undertake the cultiva- 

 tion of Capsella Bursa-pastoris Setchelliana. 



