98 



not become covered, or if the tubes lose their adhesion to each other, 

 they do not again unite, and where there are no covering tubes no 

 fruit is produced. 



In figs. 17 and 18 the central tubes, j, are long, and the covering- 

 tubes, k, I, rise half-way up one length and descend half-way down 

 another length, being met and joined by similar tubes from the joints 

 above and below, thus they are half the length of the central tubes, 

 and the studs, h, are very small, but in the very young arm, fig. 19, 

 the central tubes, j, are shorter than they are wide, and the outer 

 tubes half their length, yet the cells, h, are as round and plump as 

 they ever will be, and appear very large, being nearly of their full 

 size, and the terminal cell, i, looks gigantic, being three times as long 

 as the cells, j. 



Each of the round cells, h, forms a centre for four of the covering- 

 tubes, k, 1, as shown detached in figs. 20 and 21, and in their places, 

 18 and 22, two up and two down. Each joint may have either six, 

 seven, or eight of the studs, A, giving, respectively, twelve, fourteen, 

 or sixteen tubular cells for the circumference : twelve and fourteen 

 are the most frequent numbers. On the inner or upper side of the 

 arms there are more studs at the joints, four elongating into sprouts, 

 among which the globular blossom, n, and the seed, a, grow. 



These covering-tubes fit so closely to each other as to form a sound 

 case, yet carbonate of lime will occasionally crystallize under them, 

 showing their connexion with the plant to be at the studs, h, only. 



The cells, c, on the primary tubes of the main stem, have the usual 

 lining, paved with minute, mostly round, green vesicles, darker in 

 colour, and sd closely placed, that we can scarcely see anything 

 moving within, and they have a smaller cell, d, under them. The 

 studs, h f on the arms, in these particulars, are like them, but under 

 them, around the joints, are peculiar clear cells, with no fixed 

 vesicles : these are filled with round green vesicles, in quick circu- 

 lation, and from the largest of these cells the blossom and fruit grow. 



A number of the peculiar cells also within the large knots, close 

 under the clusters, g, are filled with circulating globules. 



On this part of my subject I have first to notice that the marked 

 difference of these cells is, that whilst the chief portions of the plant 

 have a nearly colourless fluid, in which are various sizes and forms of 

 particles, and a lining, on which elongated, green, fixed vesicles are 

 disposed as it were in regular spiral order, the fluid following their 

 course, the peculiar cells appear to have no such fixed vesicles, but 

 are filled with green globules, of regular size, and in quick circulation. 



