110 



far from presenting anything strange or anomalous, is regu- 

 larly to be observed in the gradual communication of meris- 

 tematic activity from the cambiums of two adjacent fibro-vas- 

 cular bundles to the parenchyma of the primary medullary 

 ray which separates them, or in the development of the peri- 

 derm through long stretches of the parenchymatous tissue of the 

 cortex. For the correctness of this supposition in regard to the 

 origin of the anomalous meristem in question , the fact that 

 it is not preceded or accompanied by primary fibro-vascular 

 tissue of any kind, but arises directly from the cells of the 

 pith, clearly argues. Decisive evidence however on this point 

 may be obtained by tracing the development of the cambium 

 at the nodes. For if a node be investigated from a part of 

 the stem where the secondary thickening has already begun 

 but the anomalous meristem has not yet appeared, it will be 

 found that the ends of the normally oriented cambium in the 

 regions c c PI. XVIII Fig. 4 have already begun to extend them- 

 selves inwards through the openings o in the fibro-vascular 

 ring toward the centre of the stem. If older nodes be exami- 

 ned the process will be found to progress further and further 

 until the meristematic activity reaches the pith. It here deve- 

 lopes bot/t upward and downward into the adjacent intermodes; 

 so that it is thus possible to find internodes which, in cross- 

 sections made near their upper or lower ends, exhibit clearly 

 formed, anomalous cambiums, while these formations near the 

 middle of the internode are either entirely wanting or have 

 developed to a much less extent. 



As the relations of the outer and inner cambiums are now 

 clear, it may well be asked, what connection exists between 

 the mature secondary tissues of the pith and those of the 

 normal fibro-vascular ring. While in Tecoma mdicans, as Weiss ') 

 has shown, the meristem within the nodal openings of the 

 fibro-vascular ring gives off both xylem and phloem in consi- 

 derable quantities, which form oblique strands or bundles 



1) 1. c. 



