cook: tribroma, a new genus of trees 287 



the Old World. Among them are some that are unusually inter- 

 esting in that they perhaps throw some light on the problem of 

 the origin of fall blooming in witch-hazel. On the Agricultural 

 Grounds in Washington there is a specimen of Cornus Mas with 

 a peculiar blooming habit. Every fall this tree blooms more 

 or less abundantly and in many cases sets good fruit. An inter- 

 esting feature is that not all the buds in an umbel covered by 

 the same set of bud scales will necessarily develop into fall 

 flowers. Many umbels hold some of the buds until spring, so 

 that we have fall fruit and spring flowers existing in the same 

 umbel (fig. 1). Apparently the tree is in a satisfactory trans- 

 sition condition between spring and fall blooming from which 

 the development of a fall blooming form could be easily accom- 

 plished by gradual changes in future generations. This perhaps 

 sheds some light on the development of the fall flowering of 

 witch-hazel without the necessity of a sudden mutation or with- 

 out the necessity of moving its blooming period gradually through 

 the winter months. . 



BOTANY. — Trihrojna, a new genus of tropical trees related to 

 Theobroma. O. F. Cook, Bureau of Plant Industry. 



In connection with a study of the branching habits of llieo- 

 broma cacao, attention has been given" to a related tree known 

 in Guatemala as patashte, which afl"ords a still more striking 

 example of the phenomenon of dimorphism of branches. ^ The 

 patashte tree has been placed with the cacao hitherto as another 

 species of Theobroma, under the name Theobroma bicolor, but 

 after a somewhat detailed comparison of the two trees in eastern 

 Guatemala in 1907 it did not appear reasonable to assign them 

 to the same genus. This opinion was strengthened during an- 

 other visit to Guatemala in the spring of 1914, and it is now 

 proposed to treat the patashte tree as the type of a new genus. 

 The distinctive characters are stated in the following description: 



1 Cook, O. F., Dimorphic Branches of Tropical Plants: Cotton, Coffee, Cacao, 

 the Central American Rubber Tree, and the Banana. U. S. Department of Agri- 

 culture, Bureau of Plant Industry, Bulletin 198. Pp. 39. 1911. 



