72 Botanical Societij of Edinhiirgli. 



tion, and the zones of the cultivation of useful plants, as limited by 

 altitude and latitude, shown in the elevation of the principal mountains 

 of Europe, Asia, and America, accurately laid down by scale from 

 the writings of Humboldt, jNIeyen, Boissier, Hooker, Watson, &c." 



Professor Balfour exhibited specimens of Lastrea cristata, and var. 

 uUginosa, Lastrea spinuJosa and Polystichian ancjulare, and made 

 some observations regarding them. 



The following papers were read : — 



1. "On the Development of Tubular Structure in Plants," by R. 

 Hobson, M.D. Cantab. Communicated by Dr. Balfour. 



The object of this paper was to show the mode in which tubular 

 structure is formed by the aggregation of cells in a linear series and 

 the subsequent absorption of the partition-walls. The structure 

 selected for observation was the moniliform hair found on the claw of 

 the spurred petal of Viola tricolor. The author stated, that " If the 

 structure of the tube is traced under the microscope from the root 

 or base upwards, the lower part will be found fully formed (tubular), 

 having gradually substituted a tubvdar for its previously cellular for- 

 mation. A little higher up, absorption of the partition-walls (the 

 united portion of the cells) is yet incomplete, being in transitu from 

 cell into tube, whilst the remaining part is entirely cellular to the 

 extreme point, which point is, in fact, a simple cell. 



" There may be distinctly seen in a portion of this multicellular 

 tube, near to its base, marks sufficient to prove that those points of 

 the cells which have been primarily in unioir to form the tube have 

 now been absorbed, or in some other way removed, and that this ab- 

 sorption or removal has taken place precisely in an equal degree from 

 the centre of the different septa, or united portions of the cells, to- 

 wards the periphery of the tube to the extent required to perfect 

 nature's 'handiwork.' The marks to which I allude are triflingly 

 apparent annular contractions." 



The author made some observations, also, as to the time occupied 

 in the formation of the tubes. He remarked :— 



" In order to ascertain whether the mutation of cell into tube 

 occupied much time, I instituted a comparison between the tubular 

 portion of the hair on the full-blown flower, and that on the flower 

 just opening, and found that the lower portion of the tube on the 

 former (the full-blown flower) had generally become tubular to the 

 amount of from eight to ten cells in each hair, which usually con- 

 sisted of from twenty-five to thirty cells, whilst that of the latter (the 

 opening flower) had become tubular only to the extent of about two 

 or three cells. It therefore seems that the time occupied between 

 the first opening of the flower and its fading period is sufficient to 

 convert six or eight cells into tube, and it is probable that in the 

 earlier part of the season during more genial weather, the fading 

 stage would be delayed, and consequently that in proportion as 

 the blooming period is prolonged, the length of the tubular formation 

 would be increased ; but it seems doubtful whether these tubes ever 

 became tubular throughout their entire length. 



" On the two contiguous petals on the inner and inferior part of 

 each, on a prominence where the claw takes its origin, there is a 



