518 SUPPLEMENTAllY OBSERVATIONS 



never observed the protnicled thread of the Ovuhiiii until 

 after the secondary nucleus or Embryo, of which it is 

 a continuation, becomes visible, I consider it as a produc- 

 tion subsequent to impregnation. 



It is possible, therefore, tliat the nearly similar tubes 

 which have been observed terminating, as it is supposed, 

 tlie nucleus of the imimpregnated Ovulum in a few other 

 Families, may in some of these cases be of like origin. 

 2] To the observations formerly made on the general 

 structure of Orchideae, I have here to add, — 



1st, 'Jliat the cells of the testa of the ripe seed are fre- 

 quently spirally striated, though these cells in the Ovulum 

 before and even for some time after impregnation are abso- 

 lutely without striae. 



2nd, The Fibrillse constituting the pubescence frequently 

 produced, and in some cases entirely covering the surface 

 of the aerial roots, as they have been called, of the parasi- 

 tical portion of the Order, are very remarkable. 



These FibrillsR, which I have examined both in dried and 

 recent specimens of several species, but more particularly 

 in the living state in Renanfhera coccinea, are simple 

 tubular hairs without joints, and whose apices, by which 

 they adhere when attached to other bodies, are either of 

 the same diameter, or somewhat dilated ; and then, as in 

 ■Renanthera, often more or less lobed. 



In their natural state they exhibit, in most cases, hardly 

 any indication of spiral structure; but the membrane, of 

 which they entii-ely consist, is sufficiently elastic to admit of 

 being extended, and at the same time unrolled, to about 

 twice the length of the Tube. They then form a broad 

 ribbon of equal width throughout, and spirally twisted 

 from right to left, — a direction opposite lo that which 

 generally obtains in spiral vessels. It is possible that this 

 may not be the direction of the spire in all cases ; it is 

 manifest, however, very generally, if not universally, in 

 Renanthera. 



The existence of spiral tubes produced on the surface is 

 probably of very rare occurrence ; and among Phaenoga- 

 mous plants I have hitherto met with it only in the hairs 



