the Pitted Tissue of Plants. 99 



tube gives the prismatic or angular appearance to many of 

 these tubes, so readily perceived when two vessels press 

 against each other. In some few cases a large number of very 

 small cells appear to act in compressing as a single large one. 

 When I first noticed the transitions above described I ima- 

 gined they were confined to the Ferns only, but I have since 

 found them applicable to all the plants above enumerated. A 

 very common cause of the beaded appearance on the margins 

 of tubes viewed under the microscope is their longitudinal sec- 

 tion, so that the projecting extremities of the cut fibres pro- 

 duce the peculiar appearance of beads. 



I cannot refrain here from making a few observations on 

 the remarks made by Dr. Willshire* relative to the function 

 of some starch particles, or of starch particles existing in the 

 laticiferous vessels. He says, a Dr. Barry has demonstrated 

 the existence of primordial fibre or filament in bodies of ani- 

 mal organization, and we shall endeavour to draw an analogy 

 between some of his views with phaenomena known to exist 

 in the vegetable kingdom." I think, that before any analogy 

 be attempted to be drawn, the basis of that analogy ought to 

 be established : this has certainly not been done in the present 

 instance. The appearances observed by Dr. Barry in the blood, 

 are, I think, totally misinterpreted ; and 1 am happy to find 

 Dr. Willshire comparing the fibre of the blood-disc to a dark 

 line on a piece of starch, for I am convinced that it is not a 

 fibre at all. I believe the appearance alluded to is in all cases 

 produced after the vitality of the blood is destroyed, and is 

 dependent on physical causes alone for its production. The 

 blood-discs are sacs containing the colouring matter of the 

 blood and a liquid, which is most probably the same as the 

 liquor sanguinis. Dr. Barry says, " the filaments may be 

 discerned without any addition whatever, if the coagulation 

 has begun, provided its appearance be familiar," &c. I be- 

 lieve that the sac is generally cracked at the time of the pro- 

 duction of the fibre, and the contents coagulated, either by 

 the causes producing the ordinary coagulation of the blood, or 

 by the imbibition of a portion of corrosive sublimate when that 

 is used. Moreover, I am at a loss to understand how the 

 "fibre" is primary or primordial. Dr. Barry says, "in the 

 mature blood-corpuscle there is often to be seen a flat fila- 

 ment or band already formed within the corpuscle." " This 

 filament is formed of the discs within the corpuscle." So 

 that here we should have the discs performing the part of 

 cytoblasts to the blood-corpuscle or cell, as in vegetables; 

 and the fibre must be secondary, not primary. 



I think we are bound to believe that the appearances ob- 

 * Annals of Nat. Historv, loc. cif. 

 H 2 



