578 ROSACEAE Primus 



sembles R. Carolina L." "R. relicta begins to flower earlier than R. suffulta, 

 just after R. blanda and continues to flower through the summer." Like the 

 next species, it may have originated by natural hybridization. 



8. Rosa rudiuscula Greene. Map 1181. This rose is intermediate be- 

 tween Rosa Carolina and Rosa suffulta, and has been produced experi- 

 mentally by Dr. Erlanson by crossing these species. Because of its hybrid 

 nature it is difficult to identify unless one is familiar with our wild roses. 

 In former accounts of the genus the tendency of Rosa rudiuscula to have 

 thick, leathery leaves has been stressed. This characteristic is also found 

 in Rosa Carolina and is not invariably present in the hybrid. 



According to my records this hybrid grows only in prairie habitats 

 where it is more or less frequent, especially in the northern parts of Benton 

 County and in the southern part of Jasper County. 



Ind. to Mo. 



3396. PRUNUS [Tourn.] L. Cherries and Plums 



Fruit velvety-tomentose; stone deeply sculptured and pitted; flowers subsessile, large, 

 pinkish, appearing before the leaves. (See excluded species no. 382, p. 1064.) .... 



P. Persica. 



Fruit glabrous; stone not sculptured; flowers pedicellate, smaller than the preceding, 

 white (rarely some pinkish). 

 Flowers in umbel-like clusters or somewhat corymbose, appearing before or with 

 the leaves on branchlets of the preceding year. 

 Margins of leaves cut about 1 mm deep with sharp teeth; teeth not ending in a 

 gland; fruit red; stone compressed. 

 Petioles glabrous beneath; branchlets glabrous; lower surface of mature leaves 

 glabrous or rarely more or less pubescent on the principal veins; pedicels 



and calyx tube glabrous 1. P. americana. 



Petioles more or less pubescent all around; branchlets puberulent, rarely be- 

 coming glabrous in autumn; lower surface of mature leaves pubescent all 



over; pedicels and calyx tube more or less pubescent 2. P. lanata. 



Margins of leaves cut less than 1 mm deep with blunt or crenate teeth; teeth 

 ending in a gland. 

 Teeth of the middle of the blades 10 or fewer per cm; calyx lobes glandular 

 except in no. 7; fruit more than 10 mm in diameter. 

 Calyx lobes ciliate but not glandular. 



Leaf blades generally much paler beneath; at least the basal third of the 

 margins entire and crenate above; fruit black, about 14 mm in diameter; 



surface of stone marked with oblique grooves 3. P. pnmila. 



Leaf blades not paler beneath or only slightly so; the entire margins regu- 

 larly and finely crenate; fruit bright red, globose, about 13 mm in 



diameter; surface of stone rugose 4. P. an gusti folia. 



Calyx lobes more or less glandular-ciliate. 



Calyx lobes glabrous on both sides or with a short band of hairs at the 

 base within; leaves dull, dai-k green above, abruptly pointed at the 

 apex; flowers more than 17 mm in diameter; petioles mostly with 



two glands at the summit 5. P. nigra. 



Calyx lobes pubescent both within and without; leaves lustrous above, thin, 

 acute or acuminate at the apex; flowers less than 17 mm in diameter. 



6. P. hortulana. 



Teeth of the middle of the blades about 20 per cm; calyx lobes glandless; fruit 

 bright red, less than 10 mm in diameter 7. P. pennsylvanica. 



