97 



stem, except at their ends, and gives the most favourable opportunity 

 of observing the various circulations. All the parts of these figures, 

 12 and 13, were alive and in most healthy circulation when the draw- 

 ings were made. 



The cells, c, d, are the smallest, and the tubes, «, b y b, the largest 

 features on the stem (figs. 8, 10, 12, 13 and 27), a and b are primary, 

 being united to the stem and bearing the secondary ones, e, f; 

 yet their small cells, c, appear to be of more importance, as they are 

 well developed before the others come into sight, and are then so 

 nearly of their full size as to form almost the whole bulk of the 

 youngest buds. Their early maturity, and their being stationary dur- 

 ing the future growth of the plant, marks them as peculiar and impor- 

 tant cells, deserving of much farther examination. 



Fig. 14 represents the whole of three upper and three lower lengths 

 of covering-tubes, with their exact number of cells, correctly drawn 

 from a very young stem, but spread flat. The alternate position of 

 the upper and lower sets is also shown. Fig. 15 is a side view of one 

 length. In these figures the secondary tubes, e t f, are the smallest 

 objects, and the primary tubes, a, b, are the next in size, being 

 shorter than they are wide, and not any larger than the cells, c, yet 

 the cells, c, appear to be as complete as they are ever likely to be. 



Fig. 16 is a careful tracing from nature of a very young stem, a lit- 

 tle more advanced than fig. 14. Here the end cells of the primary 

 tubes have just passed each other, and have mutually entered between 

 the opposite secondary tubes. This avoidance of contact between 

 the upper and lower primaries is remarkable. 



There is also a series of globular cells, g, g, close under the arms, 

 which arrive at maturity very early, and their clusters correspond with 

 the arms, there being two clusters to each arm : these are shown in 

 figs. 8, 16 and 27. 



The fruit-bearing arms in their early state of maturity also possess 

 features of similar importance : these are the little studs, h, h, and the 

 terminal cells, i, which in the full-grown arm, fig. 18, are but small, 

 but in the very young arms, figs. 19 and 22, are very large in propor- 

 tion, when compared with the former. 



Fig. 17 is one arm stripped of its covering, to show the ten long 

 cells, j, j, and the terminal one, i, which compose it. Fig. 18 is the 

 same with its proper covering. 



It may now be stated that the covering tubes, k, I, are formed at 

 the same time with the central tubes, j,j, and that both grow together. 

 If in any case the central tubes or any part of them are bare, they do 



