ROSACEAE. 



131 



Pbinsepia. 

 (Family Rosaceae). 



Shrubs, with rather short su- 

 pra-axillary spines somewhat con- 

 stricted at base: deciduous. Twigs 

 long and slender, round: pith 

 moderate, round, yellowish, cham- 

 bered or finally hollowed out ex- 

 cept for annular lines about the 

 cavity. Buds solitary (or the 

 spine representing a second), 

 small, indistinctly scaly, con- 

 cealed in brown hairs that line the 

 stipules and fill the axil, the end- 

 bud lacking. Leaf-scars alter- 

 nate, small, half-round, raised: 

 bundle-trace 1: stipules rather 

 large becoming firm and persistent 

 at top of the swollen leaf-cush- 

 ion. 



Prinsepia, unlike most Rosa- 

 ceae, which have solid pith, has 

 its pith chambered or finally ex- 

 cavated, as Solereder indicates in his Systematic Anatomy of 

 the Dicotyledons. Mention of this discovery is made in a pa- 

 per on chambered or discoid pith by Foxworthy in the Pro- 

 ceedings of the Indiana Academy of Science for 1903. It is 

 one of a small group differing in a number of respects from 

 other Rosaceae. 



Some Prinsepias are sometimes called Plagiospermum, but 

 the two genera are not considered sufficiently distinct for 

 segregation by other botanists. They are among the earliest 

 shrubs to come into leaf in spring. 



Twigs becoming brown. (1). P. sinensis. 



Twigs persistently gray. (2). P. uniflora. 



