0BSEUVATI0N3 ON THE PUKPLE LABURNUM. 323 
19. Tillandsia recurvata, L. On roofs of houses. 
20. PoropJiyllum ruderale^ Cassini. {Namu,) On roofs of Louses. 
21. Polypodium incanum, S\v. On roofs of houses. 
OBSERVATIONS ON THE PURPLE LABURNUM. 
4 
By James Backhouse, Esq. 
I am not aware of the circumstances under which the Purple Labur- 
num originated, as to whether we owe it to accident or to horticultural 
skill ; but it has the reputation of being a hybrid between two plants 
of very dissimilar habit, viz. Cytisns Lahtcrniim and Cytisus purptireus. 
To the fact of these being its parents, by its throwing out branchlets 
of true Laburnum and bushes of Cyimis pti^ptireus^ it often hears in- 
disputable testimony ; and it thus also testifies against the outrage to 
nature in its hybridization. 
The Purple Laburnum is propagated by grafting on the Common 
Laburnum, but the Common Laburnum branchlets on the Purple La- 
burnum are not from the Laburnum stock, but from the branches of 
the Purple Laburnum, and often far above the union with the stock. 
And generally, if not always, a bush of Cytisua piirpio'eus is protruded 
a little below the branchlet of Common Laburnum. 
The flowers of the Common Laburnum and oi Cytisu8 purpureus 
projected from the Purple Laburnum are fertile, and I have been asked, 
if the seed from them would veo:etate? To this I can now answer on 
behalf of the Laburnum seeds, that they will. I sowed the seeds from 
two pods of Yellow Laburnum grown on a Purple Laburnum this 
summer, as soon as they were ripe, and they all vegetated. The pot 
in which they were sown was placed in my vinery, to prevent any other 
seeds getting among them by accident. I do not yet see a Cytisus 
pnrpureiis on my Purple Laburnum, but expect one, as a necessary 
consequence of the branchlet of Common Laburnum having been pro- 
duced. Within the last twenty years I have noticed many Purple 
Laburnums projecting the Yellow Laburnum and Cytism purpurens, 
but none in which only one of these was projected ; though both were 
not always projected simultaneously. The flowers of the Purple La- 
burnum are, so far as I have noticed, always barren. 
