1267 



The foliage dies down in summer but comes up again in 

 early spring or late v/inter, where the climate is mild. 

 Apparently withstands zero temperatures. Collected in 

 pockets of humus soil beneath tall trees on a rocky 

 mountain slope at an elevation of over 2, 000 feet above 

 sea level. May possibly be hardy at Washington, D.C." 

 (Meyer. ) 



Mains theifera (Malaceae), 45681. From Jamaica 

 Plain, Massachusetts. Presented by the Arnold Arbore- 

 tum. A small handsome tree with stiff spreading 

 branches, resembling a cherry tree when in bloom. The 

 fragrant flowers are white or light pink with purple 

 calyx, and the young leaves are purplish. The fruit is 

 globose, light greenish yellow with reddish cheek, 

 ripening in Massachusetts in October. The tree is A- 

 siatic in origin, ranging from China to Assam. (Adapt- 

 ed from Rehder, and also Bailey, Standard Cyclopedia 

 of Horticulture, p. 2872. 



Pavetta zimmerrnanniana (Rubiaceae), 45554. Prom 

 Buitenzorg, Java. Presented by the Director of the 

 Botanic Gardens. A small rubiaceous tree or shrub, 

 with opposite, nearly elliptic leaves and clusters of 

 small, slender- tubed white flowers. "The remarkable 

 researches of Zimmerman and Faber, detailed in the 

 Jahrbucher fur Wissenschaf tliche Botanik, vol. 51, p. 

 285, 1912, and vol.54, p. 243, 1914, make this species 

 of unusual interest. Faber has proved that the leaves 

 of this and several other species of Pavetta, Psychot- 

 ria, and possibly other genera of the Rubiaceae con- 

 tain colonies of a non-motile, nitrogen-fixing bacte- 

 rium which he names Myco- bacterium rubiacearum . The bacte- 

 ria of this species almost invariably inhabit the mi- 

 cropyle of the young seed and, when the seed germinates, 

 grow through certain stomata of the very young leaves 

 and into the intra-cellular spaces formed in the leaf 

 tissues around these stomata. Cavities are formed 

 through the growth of the epidermal cells which later 

 close entirely and make bacterial nodules which are 

 deeply imbedded in the leaf tissues. A single leaf 

 may have several dozen of these symbiotic bacterial 

 nodules. Faber was able, by treating the seeds with 

 hot water and a solution of sublimate to kill the in- 

 habiting myco-bacteri a and, later, to infect part of 

 the seedlings grown from these seeds with p Cultures 

 of the bacterium. The artificially infected seedlings 

 grown in soil free from combined nitrogen, grew well 



