1 6 Proceedings of the Royal Irish Academi/. 



with P. his-panica, and anotlier with P. cuneata. There are also two seedlings 

 at Glasnevin which are the only suvivors of a set raised for me at Cambridge 

 in 1910 from seed of a large London Plane growing near the main gate at Kew. 

 The rest of the set died from drought, having been transplanted into a field 

 in that dry year. These two seedlings are extremely imlike in foliage : one 

 has leaves indistinctly lobed resembling those of /'. occidentalis. The other 

 has deeply lobed leaves, and differs little from P. cuneata. See Plate YIII, 

 fig. 8. 



Several unsuccessful attempts have been made since 1910 to raise a 

 numerous set of seedlings of the London Plane with the object of studying 

 the botanical characters of the various classes which are wont to occur in the 

 second hybrid generation. Space for such experiments is scarcely available, 

 as planes do not assume for several years their adult foliage, and do not pro- 

 duce fruit till they are twenty or thirty years old. 



The artificial production of a cross between P. orientalis and P. occidentalis 

 has not been possible in thiscountry, where there exists no adult living tree 

 of the latter species from which pollen oould be obtained. An attempt to re- 

 produce /'. acfrifolia by cross-pollination of the Occidental and Oriental 

 Planes might be made in the United States, using the native tree as the 

 female parent 



A descrii)tion of the two parent species, as well as of P. aceri/olia and its 

 descendants, will now be given in detail, supplemented with some information 

 concerning the occurrence of the latter in cultivation. 



1. Platanus orientalis, L. Oriental Plane. 

 Plate V, fig. 1. 



A large tree, with wide-spreading branches. Leaves moderate in size, six 

 to seven inches across, with five distinct lobes extending at least half way 

 to the base of the blade, oblong-triangular, entire or toothed; base of the 

 blade usually truncate, with a central cuneate part ; main nerves arising at 

 some distance above the junction of the petiole with the blade ; tomentum 

 usually falling off, so that the blade and petiole are glabrous at the end of the 

 season. Fruit-balls 2-7, bristly, averaging one inch in diameter ; achene with 

 a short tomentose body anrl a conical tomentose bead, prolonged into a per- 

 sistent style. 



The above description applies to trees indigenous in Greece and Asia 

 Minor. Most of the trees cultivated in England are of this origin. The leaves 

 of the trees cultivated in Kashmir and Persia are much larger, with broad 

 oblong-triangular segments, indicating perhaps a distinct race. A small- 



