THE RECEPTACULAR TUBE. 



97 



an outer epidermis, and an intermediate ground tissue, 

 apparently nearly uniform in character, from one epidermis 

 to the other (as in Fig. 14, a to e, p. 68). A definite number 

 of fibro-vascular cords jDeneti^ates this ground tissue. Theo- 

 retically, if this structure consist of two parts, viz. the 

 interior carpels and the exterior "tube," some line of 

 demarcation might be expected to be traceable ; but in the 

 majority of cases it would seem that, as neither the inner 

 epidermis of the tube nor the outer one of the carpels are 

 required, they are not developed at all ; and so the internal 

 tissues of the two organs become confluent and uniform, and 

 this accounts for the fact that the dorsal cords at least are 

 simply embedded in this common tissue. Nevertheless, in 

 some cases there actually is a certain differentiation in the 

 tissue, as Van Tieghem has shown in the case of Alstrcemeria 

 versicolor (Fig. 30), where a yellow band of cells marks the 



Fig. 29. — Receptacular tube and 

 calyx-limb of Cherry. 



Fig. 30.— Alstrcevieria (after Van 

 Tieghem). 



junction or congenital fusion of the two parts (indicated by 

 the line in the figure). 



From the preceding descriptions, it will be seen, with 

 regard to the sources of the cords belonging to the inner 

 whorls, that they arise by division, radial or tangential as 

 the case may be ; and then the secondary cords thus parted 

 off are generally included within the tissue of the tube. 

 11 



