February 27, 19* 19 3i 



"Sir Joseph Hooker adopted the connate theory, and says: 



"'The anomaly of the single-leaf is due to the cohesion of 

 the two semi-terete leaves of each sheath, and is far from being 

 a constant character. In the plants at Kew the two leaves are 

 as often free as united, and on making a transverse section it will 

 be seen that the vascular bundle in the center of the cylinder is, 

 in fact, double, and that the two parts are sometimes separate.' 



"Maxwell R Masters, editor of the 'Gardner's Chronicle,' 

 London, in 'Annals of Botany,' Vol. II, No. 5 (kindly loaned me 

 by Professor Greene), discusses the phenomenon very plainly, 

 and, as he arrives at a different conclusion from the above emi- 

 nent authority, it will be of interest to present his statements 

 briefly in this paper. After stating that 'the axial or ramial na- 

 ture of the typical pine needle is now pretty generally discred- 

 ited;' he writes: 



" 'In the hope of reconciling the discrepancies between these 

 statements, or of ascertaining which is the nearest to truth, I 

 have recently repeated some observations first made in 1883, 

 both as to the minute anatomy of the leaves and to their mode 

 of reproduction.' Then follows a detailed description of the 

 micioscopic organs seen in a cross section of a leaf of the Punts 

 monophylla^ showing that the structure is in all respects the same 

 as in the leaves of other pines: 'hence,' he concludes, 'the leaf- 

 like body is a true leaf which occurs singly usually, but occa- 

 sionally in pairs; as must have been the case of the leaves ex- 

 amined by Sir Joseph D. Hooker. There is, of course, no diffi- 

 cult)' in understanding the latter condition; the anomaly con- 

 sists in the single cylindrical leaf, to all appearances occupying 

 the apex of a shoot. 



" 'To clear up this anomaly I investigated the development 

 of the constituent parts of the leaf bud at various stages of 

 growth, and, without going into details, I may say that develop- 

 ment supplied the clue which neither outward morphology nor 

 internal anatomy sufficed to give. In point of fact, in the earl- 

 iest stages examined there were always two foliar tubercles, one 

 of which speedily overpassed the other, so that ultimately all 

 traces of the second leaf were obliterated. The monophyllons 



