Dr. Wiltshire on some points of Vegetable Structure. 45 1 



of evidence of secondary formation being thus derived in 

 most plants and but little of primary, yet in others the cir- 

 cumstances of the case are such as to lead us to believe in the 

 origin of the general tissues being derived from primary spiral 

 filaments. In a new species of Stelis brought by Meyen from 

 the island of Lucon scarcely any membrane is to be found not 

 so resolvable, and surely this or much of it must be primary. 

 In the description of this plant the physiologist just men- 

 tioned states that all the parenchymatous cells lying beneath 

 the epidermis are composed of tissue formed by spirally wound 

 bands, and possess no otherwise primary homogeneous enve- 

 loping membrane. In some of the larger cells where pres- 

 sure is exerted, as at their terminations, the membrane ap- 

 pears structureless or homogeneous like ordinary membrane, 

 but all the rest of them is distinctly formed of spiral filaments 

 (PL XII. fig. b.). Now, from all portions and structures of this 

 plant being so composed, save the cells of the epidermis, it 

 would appear to be a pushing of a doctrine to maintain that the 

 spiral fibre and filament are here but of secondary origin ; and 

 even the cells of the epidermis, we are inclined to believe, are 

 derived from the same element, since the parchment-like cells 

 of the aerial roots presented spiral lines, though the filaments 

 were so firmly grown together that they could not be separated 

 as a great part of the others could. 



From the universality here evinced, we think we may not 

 be in error in believing that Schleiden's theory, that the for- 

 mation of filament does not take place independently of mem- 

 brane, but occurs in the interior of cells whose membrane was 

 originally homogeneous, meets with a great exception. The 

 spiral lines observed by Dr. Brown on the hairs of Trades- 

 cantia form, we think, another. We cannot go the length of 

 Corda, who states that the shortly articulated spiral vessels of 

 Nepenthes distillatoria are devoid of an enveloping homoge- 

 neous membrane. 



In that description of tissue known to vegetable anatomists 

 by the name of fibro-cellular, there is a variety found occur- 

 ring in portions of the generative apparatus of some plants in 

 which the fibre appears totally independent of membrane in 

 its fully developed state, and has hence been called fibre with- 

 out membrane. From the investigations of some continental 

 physiologists, however, we are prevented from accepting these 

 instances as examples of primary fibrous development, and as 

 yet must regard them as examples of secondary formation only. 

 In one remarkable case, however, in which fibre occurs, in the 

 seeds of Collomia, which was first published by Dr. Lindley, 

 though Horkel is said to have demonstrated it to his class 



