THE NECTAR GLAND IN CACTI 149 



at which the disorganization of the cell contents takes place carries 

 this forward somewhat in advance of the dissolution of the cell 

 walls. The cuticle, therefore, remains adherent to the top 

 of the gland by means of the middle lamellae. It appears clear, 

 therefore, that the release of the cuticle is, in this case, merely 

 an expression of a general autolysis of the epidermis. This con- 

 clusion is strengthened on comparing the behavior above with 

 that of the following. 



Opuntia sp. 5 (figs. 12 to 15). The glands of this species are 

 exceptionally large for the cylindropuntias. Usually only one 

 occurs on an areole, though two may be found. The gland is 

 cylindrical, and flat-topped or slightly dished. We are unable to 

 find, in any of our preparations, an apical projection, such as 

 Ganong figures in his paper above cited, though such a transi- 

 tional condition as between the nectary and the thorn may well 

 occur. That tissue which occupies the whole structure above the 

 very short neck is readily divisible into two zones. The lower, 

 occupying the much greater bulk, is composed of elongated thin- 

 walled elements, among which are scattered isodiametric idio- 

 blasts containing small aggregates of calcium oxalate. The upper 

 part, doubtless the proper secretory tissue, occupies a shallow 

 zone (fig. 12, g) at the top of the gland, and is composed of spherical 

 thick-walled cells with dense contents. Calcium oxalate accumu- 

 lates here in large amounts in the moribund gland. Cutinization 

 of the epidermis is confined to the outer wall, and this is not very 

 thick. The radial and inner walls are uniformly thin. The man- 

 ner in which the cuticle is set free is seen with the greatest clear- 

 ness in the preparation from which fig. 13 was made, in which the 

 thin remnants of the secondary membranes are to be seen in a 

 state of collapse and incompleteness, empty of contents save a 

 granule or two, and attached, but only loosely, to the arched 

 cuticle. The middle lamellae cannot be seen except over the area 

 from which the cuticle has not yet been released (a, fig. 13). Here 

 they may be observed, as also the secondary membranes, in a 



5 No. 46, Lloyd, Cacti of Northern Zacatecas. This species is very similar if 

 not identical with Opuntia tunicata (Lehn) Link and Otto (No. 24, Lloyd, Cacti 

 of Northern Zacatecas). 



