Taxonomic Anomalies 675 



known to produce sucli cups from time to time. 

 They are narrower than those of the teasel, but 

 this depends, as we have seen for the " one- 

 leaved " ascidium, on the shape of the original 

 leaf. In other respects they exactly imitate the 

 teasel cups, showing thereby how these cups 

 may probably have originated. 



In numerous cases of anomalies some acci- 

 dental structures are parallel to specific char- 

 acters, while others are not, being obviously in- 

 jurious to their bearers. So it is also with the 

 double ascidia. In the case of stalked leaves 

 the two opposite stalks must, of course, consti- 

 tute a long and very narrow tube, when growing 

 together. This tube must bear at its summit 

 the conical ascidium produced by the two con- 

 nate limbs. At its base however, it includes the 

 terminal bud of the stem, and frequently the 

 tube is so narrow as to impede its further de- 

 velopment. By this contrivance the double as- 

 cidium assumes a terminal position. Instances 

 have been observed on magnolia, in Boehmeria 

 and in other cases. 



Flowers on leaves are of rare occurrence. 

 Notwithstanding this, they constitute specific 

 characters in some instances, accidental anoma- 

 lies in others. Helwingia rusciflora is the most 

 curious and best known instance. It is a 

 little shrub, belonging to the Cornaceae, and 



