Transactions. 



Stomata. 



Verv numerous in first leaves, especially in Dicksonia. The 

 mother cell is cut out from the acroscopic end of the elongating 

 cells ; auxiliary cells are absent. In the mature form (figs. 46, 

 47) an auxiliary cell is present, but there is much variation. 



Slit of stoma parallel to line of greatest growth. 



Petiole. 



Dicksonia squarrosa. 



In the first leaf there is a simple stele consisting of three or 



more tracheids grouped into a solid strand, and surrounded by 



two or three layers of parenchyma and an endodermis. The 



bundle is collateral, the few phloem 

 elements being on one side, but 

 the elements are more evenly dis- 

 tributed f r s we descend to the 

 foot. 



In later leaves the number of 

 tracheids rapidly increases, and as- 

 sumes the 

 form of a 

 shallow U, 

 with defi- 

 nite spiral 

 protoxylem 

 in the centre 

 (fig. 4). 



Diagram of Bundle 

 at this Stage. 



(a.) Phloem absent in the bay. 

 (b. ) Endodermis. (c. ) Tracheids. 

 {d.} Protoxylem group. (e.)Fro- 

 tophloom. (/.) Ptricycle, with 

 origin, with endodermis in a 

 single original layer. 



(a.) Phloem extends to 



A few leaves later the protophloem here - an( ' is not found in- 

 i • , ,i . __ side the bay. (6.)Protc- 



is broken up into three separate masses xyk . m J f J ^ rtkn 



(fig. 5). but the xylem forms a con- of pinna. (cJMfcdianp-o- 

 tinuous arc. toxylemgr< up. (d.) Xylem 



Later again the groups of tracheids elements, 

 formed round the protoxylem groups are not contiguous, and now 

 the arc is ready to break up into three separate bundles (fig. 5). 



When the stem is about J in. and the largest leaf 2 in. the 

 petiolar bundle breaks up into three separate portions, but 

 these three fuse together again before the pinnae are given off. 



protoxylem 



Q S 



OP 



£*» 



Base of Petiole. 



3 4 



J 1st below First Pinna 



Differences between the petiole at this stage and when 

 mature are unimportant, being only due to increase of size. In 



