162 BOTANICAL GAZETTE 
I. VANTIEGHEM. 
1. Protostele 
eae Sie 
2. Medullated monostele 4. Polystele 
“a ; 
3. Astele (schizostele) 5. Gamostele 
IJ. JEFFREY (USING THE SAME NUMBERS TO DESIGNATE EQUIVALENT TYPES). 
(1) Protostele 
(5 and 4) Siphonostele with internal phloem and endodermis (amphiphloic 
siphonostele) 
(3) Siphonostele with internal endodermis (ectophloic siphonostele) 
(2) Siphonostele without internal phloem or endodermis. 
It will be noticed that Jerrrey derives the vascular structures 
characteristic of the seed plants from those of the pteridophytes by 4 
process of reduction; further, he considers the pith to be simply fun- 
damental tissue which has intruded through the foliar or ramular 
gaps, while VANTIEGHEM assumes a stelar origin for the pith. 
The researches of JEFFREY (7) and GWYNNE-VAUGHAN (4) seem to 
place beyond question the view that the ferns possess an amphiphloic 
siphonostele derived from a protostelic condition by the bending in 
of phloem, endodermis, and cortex above the point of exit* of the 
foliar traces; but that the seed plants have primitively a central cylin- 
der built on this plan is a generalization which must be tested by the 
examination of representatives from a number of typical families m 
different regions of this great group. With this object in view I have 
undertaken, at the suggestion of Dr. Jeffrey, to investigate the devel- 
opment of the central cylinder in two characteristic monocotyledonous 
families, the Araceae and the Liliaceae. Such an investigation 
ought to answer the following questions: 
1. What bearing on current stelar theories has the development 
of the central cylinder in these families ? 
2. Are the amphivasal bundles found in so many monocotyledons 
to be considered a primitive type ? | 
‘For the sake of clearness the leaf traces will be treated as if they originated “a 
central cylinder, regardless of the actual direction of their development, which in most 
cases has not been made out. 
