Dr. Willshire on some points of Vegetable Structure. 453 



yet we think that the Protonemata of Turpin is not so low as 

 this, and that we cannot stop from reducing them, however 

 low they may be, into a complication of a lower form — the 

 Protospheria, and in ^hich it may truly be said scarcely any- 

 thing but the exemplification of the element can be seen. 



Though we believe then, that on an examination of our 

 knowledge with respect to vegetable anatomy, much will be 

 found in support of Dr. Barry's theory, yet much will re- 

 main, and which certainly comprises more facts than exist in 

 favour of that theory, which entitles us to maintain that tissue 

 exists not derived from primary filament, and that the latter 

 is in a great mass of cases a secondary formation only. While, 

 therefore, we would modify some statements made in the ob- 

 servations on the structure of Tilia^ at p. 85, by substituting 

 for " all tissue " " much tissue," and admitting that some 

 membrane is composed of primordial filaments, we cannot 

 attach less importance to the doctrine of a secondary fibrous 

 layer there maintained. 



The next point to which we shall allude is in reference to 

 the formation of the punctation on dotted vessels. With de- 

 ference to Mohl, whose views however we may have not pro- 

 perly made out, from the foreign language in which they are 

 propounded, we beg leave most decidedly to differ, and be- 

 lieve that the origin of the punctations is immediately depend- 

 ent upon a fibrous layer ; and from an analogy alluded to 

 by Dr. Barry, and a suggestion of his with regard to the teeth 

 of a spiral filament being concerned in their production, we 

 hold that the matter may be properly explained : on the other 

 hand, we must remain in the opinion of Schleiden, in oppo- 

 sition to that of Dr. Barry, whom we consider to look upon 

 these fibres as primary, that this fibrous layer is of secondary 

 origin ; that it is formed within a previous homogeneous mem- 

 brane which alone is primary. 



In all vessels in which true punctations are found, whether 

 the central dot is suiTounded by a circle or not, or whether 

 the circle alone exists, the first approach to their formation 

 is the production of a secondary layer of fibres upon the 

 inner surface of the apparently primary homogeneous mem- 

 brane. This layer consists of filaments, which not only have 

 a spiral direction with respect to the duct in which they are 

 formed, but they are bent upon themselves as it were, forming 

 sinuous curves (PI. XII. fig. c. («)). In many cases the posi- 

 tion of these filaments with respect to each other is such, that 

 the directions of the cur\'es are opposed to each other (as at fig. 

 c.{b)), and in all very densely punctated vessels such appears 

 to be the case : on the other hand, the bendings of the filament 



