35 ELEMENTARY ORGANS. CHAP. III. 



the centre of the trunk, and clear of divergent 

 layers ; and the tubes seemed to appear most dis- 

 tinct when the slice was so placed as to present 

 their longitudinal dimensions to the light. They 

 seemed to resemble ribands wrapped spirally 

 round a cylinder rather than to form separate 

 vessels, which corresponds very well to their ap- 

 pearance even in the succulent parts of many 

 plants, as described by Knight. Some of them 

 seemed even separate and entire. And yet upon 

 repeated observation I have not been able to satisfy 

 myself entirely on this point, though I have ven- 

 tured to state the case circumstantially, as being 

 the probable means of inducing some one to take 

 up the subject who may be more felicitous in his 

 investigations. It cannot be said to be a vain or 

 fruitless inquiry. For as they are known to have 

 existed at least in the tender shoot, it will follow 

 that they must exist in one shape or other in the 

 matured wood also. And if their spiral form is 

 there obliterated, under what other aspect do they 

 now appear ? It seems certain from the observa- 

 tions of Hedwig, that they assume a different figure 

 in different stages of the plant's growth. In the 

 peduncle of the Colchicum autumnalc, the rings 

 of the tubes are closer when it begins to appear 

 above ground, than at the time of flowering ; from 

 which he concludes that they are at length entirely 

 obliterated, and the tubes converted into woody 

 fibre. But sometimes it is difficult to detect them 



