810 THE STRUCTUEE OF FLOWERS. 



" Les bulbilles des Amaryllidees ne sont pas toujours des 

 graines veritables modifiees seulement quant a I'epaisseur et 

 a la consistance de leurs diverses couches naturelles, notam- 

 ment des phis esterieures. Temoin le Calostemma Cunning- 

 hamii. Ici, par una singuliere transformation de I'ovule ea 

 bulbe, la cbalaze, en s'epaississant, joue le role d'un veritable 

 plateau, sur leqnel se prodiiisent une, puis plusieurs racines 

 adventives. Les enveloppes ovulaires tienne alors lieu 

 d'ecailles bulbaires tandis qu'il s'eleve dans le sac embryon- 

 naire un veritable bourgeon parti de la chalaze comma 

 sujDport et s'echappant par son sommet de la cavite ovulaira 

 pour se comporte eusuite comma une plante complete." 



An analagous case of bulbs arising from a foliar organ 

 occurred with Scilla Sibirica. Some plants dug up in October, 

 1887,* were found to have taken the form of the so-called 

 " droppers " not uncommon in tulips. Their peciiliarity 

 resides in the fact that the tubular leaf-sheath bends and 

 grows downwards, thereby carrying the axillary bulbil to a 

 greater depth in the soil than usual. In February, 1888, on 

 re-examining them, Dr. Masters discovered that from one to 

 four bulbils had been developed at different heights within 

 the tissue of the tubular sheath, being in connection with the 

 cords of the latter by means of a transverse nexus of tracheids. 



I refer to these cases as being curious instances of axial 

 structures proceeding from foliar — i.e., by the change of 

 character of the fibro-vascular cords from being at first 

 foliar and then axial. They support the theory of homology 

 of leaf and axis, which is, of course, otherwise quite efficiently 

 substantiated by such plants as XylopJiylla, Huscus and the 

 Cactacece. 



* Gard. Chron. for Oct. 15, 1887, p. 475, fig. 98, " droppers ; " also, for 

 March 3, 1888, p. 27S, fig. 45, ditto, with bulbils. 



