48 



Robinson : Spines of Fouquieria 



In Idria, another genus of the same family, a similar spine, 

 originating in the petiole of the leaf, has been described by Poisson 

 (Bull. Mus. Hist. Nat. i : 278. 1895) and in some species of the 

 nearly related Cantua, of the Polcnioniaceae, there is a woody ridge 

 at the base of each node. The latter, however, is more like the 

 structure which protects the axillary bud in Syrhiga and Philadel- 

 phus than the spines of the Fouquieriaceac. 



The majority of the buds in the axils of the primary leaves do 

 not elongate to form branches, but develop small clusters of spat- 

 ulate leaves which are almost sessile and do not form spines 

 (Figs. 1 1 and 12, <r). 



Engelmann (Bot. Gaz. 8: 338. 1883) was the first to call 

 attention to this peculiar mode of dehiscence of the leaves of Fou- 



FlG. 10. Fouquieyia Maaiongalii, shQvimg a, manner of dehiscence of leaf ; k, 

 manner in which spine and bark may be peeled from stem. 



Fig. 1 1 . Young shoot of Fouquieria Macdougalii. c, cluster of secondary leaves ; 

 7V, thickening which will form spine. 



Fig. 12. Young shoot of Fouquieria splendens. 



Fig. 13. Spine of Fouquieria Macdougalii. d, surface from which upper portion 

 of petiole has separated. 



quieria. Plank (Garden & Forest, 9: 73. 1896) says: "The 

 bases of the spines appear to arise in the cellular part, leaving the 

 wood full of holes in their decay," which statement was doubtless 

 made because of the peculiar growth of the cork between the 

 spines and the portions of the outer tissues, which adhere to 

 them, making the spines, with their adhering pieces of bark, dry, 

 papery structures, which still have close enough contact with the 

 adjacent cells to leave a scar when they drop off. Van Tieghem 



