THE PINES OF MEXICO. 



3. PINUS NELSONI SHAW 



PlNUS !Nelsoni Shaw, Gard. Chron. ser. 3, xxxvi, 122, fig. 49 (1904); xxxvii 306, fig. 127 



( 1905-) 



Leaves with persistent sheaths, connate in fascicles of 3/6-9 cm. long, serrate on the two 

 dorsal margins; stomata dorsal and ventral ; resin ducts external. Cone" s on long, stout 

 curved peduncles, symmetrical, cylindrical, opening at maturity, early deciduous; apophyses 

 deep orange-red, elevated in the middle to a sharp transverse ridge culminating in a dark 

 indefinite umbo. Seeds wingless, pale ochre-yellow when fresb, with a faint reddish area at 

 the apex. Branchlets long, slender, pliant, very tough, their bark persistently smooth and 

 gray. Buds covered with resin. 



A low bushy tree not exceeding 8-10 metres in height, with long, slender branches clothing 

 the trunk to the ground and sparse gray-green foliage, growing in a limited area on the lower 

 slopes of the north-eastern Sierras where it is associated with P. cembroides. 



Nelson 4501 (398615) Miquihuana, Nuevo Leon Pringle, 10016 Shaw, San Lorenzo, Nuevo Leon. 



Seedlings raised in the Arnold Arboretum reproduce invariably the connate leaf-clusters. The ventral surfaces 

 of the three leaves, forming each fascicle, are partly grown together and successfully resist the action of alcohol, 

 turpentine or alkaline solutions, but are easily forced apart by rolling them between the fingers. A narrow 

 portion of each ventral surface is free and contains a single row of stomata. 



The branchlets continue their growth throughout the summer, and the female aments which, at the time of pollina- 

 tion were subterminal, had become, by reason of this growth, pseudolateral conelets in November when I saw them. 

 The conelets, after pollination, continue to grow and attain, in November, considerable size. This peculiarity 

 appears to be normal with this species and cannot be explained by unusual conditions of locality or season, for 

 the conelets of P. cembroides, which grows side by side with P. Nelsoni at San Lorenzo, like those of all other 

 Pines, had made no growth during the summer. When the cone falls its large curved peduncle remains on the 

 tree for some years but the cone itself rapidly disintegrates. 



The nuts are greedily eaten by macaws, and are found exposed for sale in the markets of Victoria, Tamaulipas 

 and of Matehuala, San Luis Potosf. 



Fig. 1. Cone scale and seed. 

 " 2. Open cone, San Lorenzo. 

 " 3. Persistent sheath, magnified. 



PLATE III 



Fig. 



Branch, conelet and leaves. 

 Leaf section, magn. 30 diam. 

 Closed cone, San Lorenzo. 



