PREFACE. 
Wira regard to the old opinion of spiral vessels 
being confined to flowering plants only, it may be re- 
marked that they have been found in Lycopodiacez by 
Mr. Valentine. Indeed, they exist in abundance, sim- 
ple and compound, in the gyrate portions of the 
rachis in many, perhaps all Filices; not that their pre- 
sence depends on this gyration, but on the later deve- 
lopment of these parts: since it is found that nothing 
but ducts are present in the older parts of many PEU 
while they occur with spiral vessels in the younger. —— 
"This was a mere assumption and until all and every. 
link € MA deber tne ie iy a 
eus as afc We BE od. iouslituent of the . 
latter to be esexual because as yet we are ec 
ignorant of their reproductive organs. — 
That the age of Ede vec dein know 
