improvement of, ii. [216].
Pinus pumilio, Mughus, and nana, varieties of P. sylvestris, i. 363.
Pinus sylvestris, i. 363, ii. [310];
hybrids of, with P. nigricans, ii. [130].
Piorry, on hereditary disease, ii. [7], [78].
Pistacia lentiscus, ii. [274].
Pistils, rudimentary, in cultivated plants, ii. [316].
Pistor, sterility of some mongrel pigeons, i. 192;
fertility of pigeons, ii. [112].
Pisum arvense and sativum, i. 326.