Dr. Willsbire on some points of Vegetable Structure. 449 



indicating the hollow or excavation which lies between the 

 vessels, and the apparent fibres which include the meshes are 

 produced by the position of the vmlls of the vessels J" From this 

 it would appear then, that there is no distinct secondarily 

 formed layer of fibrous network, but that the peculiar posi- 

 tion of the walls of the vessel against adjacent lying struc- 

 tures gives rise to hollows or excavations, the circumferential 

 edges of which constitute the fibres of the apparent net. If 

 this proposition be really what is meant, the theory of the cir- 

 cle of the punctation [der Hofdes Tupfels), according to Mohl, 

 is nothing further than a depressing of the primary homoge- 

 neous membrane in certain places. It is true, that the writer 

 admits of the existence of a secondary layer, and also of fibres 

 running between the punctations in certain descriptions of ves- 

 sels, but this layer is not, he says, composed of spiral fibres 

 grown together, nor have these fibres anything to do with the 

 formation of the circle of punctation. How mere local posi- 

 tion can give rise to such symmetry, peculiarity of form and 

 spiral appearance which the dots and circles of punctated 

 ducts really possess, it is to us difficult to imagine, as also 

 what truly should be deduced from MohPs own statement 

 upon the subject. We would beg to offer a few remarks con- 

 nected with this matter as suggested by our own observations 

 as influenced by the recent investigations of Dr. Barry on the 

 presence of primordial fibre. Dr. Barry has demonstrated the 

 existence of primordial filament or fibre in bodies of animal or- 

 ganization, and we shall endeavour to draw an analogy between 

 some of his views with phaenomena know^n to exist in the 

 vegetable kingdom. The point from which we shall start is, 

 that in that fluid of animals which plays the part of a mediate 

 agent in nutrition, and offers to the plastic powers of the ul- 

 timate cells a generative structural material, it has been 

 shown corpuscular bodies exist possessing a peculiar filament 

 or fibre, and which, through the kindness of Dr. Barry, I had 

 an opportunity of seeing at the College of Surgeons. This 

 gentleman remarks, that it is well known that discoid bodies 

 circulate in plants, and it remains to be shown whether they 

 have not filaments, and whether the spiral filamentous deve- 

 lopment i^ primary (Ann. N. Hist. vol. viii. p. 503). The juice 

 circulating in the lactiferous tissue of vegetables contains cor- 

 puscles and variously shaped bodies, of which Ficus, Vinca, 

 Chelidonium, &c., will afford illustrations. In certain species 

 of Euphorbia, however (Meyen, 'Pflanzen Physiologic,' vol. ii. 

 p. 394 et seq.), exist strangely and differently shaped objects 

 circulating in the milk juice, and in which dark stripes or lines 

 may be observed (PI. XII. fig. a.) : these I hold to be analogous 



