104 



that among the normally oriented secondarj'- tissues, where, 

 as will be remembered, the anomalous structure arose from a 

 localized production of hard and soft xylem (corresponding to 

 the „Zackenholz" and „Holzausfullung'' of Phytocrene), this 

 anomaly does not become more pronounced with the age of 

 the internode but, on the contrary, tends gradually to dis- 

 appear. The portions of the cambium , which before produced 

 only soft elements, begin to give off tracheids and vessels, 

 which form a tissue much like the wood of the lobes, from 

 which it differs only in the greater breadth and frequency of 

 medullary rays. This altered growth proceeds so rapidly that 

 the contour of the stem soon becomes rounder and the ellip- 

 tical form is finally scarcely noticeable , the maximum diameter 

 being not more than a tenth greater than the minimum. The 

 production of the normal bast is abundant around the entire 

 circumference of the stem but especially so from the parts of 

 the cambium surrounding the prominences of the xylem. As 

 new cribrose tissue is developed the older, outer sieve-tubes 

 collapse, leaving only the cambiform cells and medullary rays 

 forming long cell-rows, which soon become much bowed and 

 distorted by pressure from the younger still growing tissue. 

 In spite of this continued production of bast and successive 

 destruction of the older sieve-tubes , there is no formation of 

 a scale-bark, the first-formed periderm continuing its centri- 

 petal growth without the development of inner periderms. 



The formation of the bast in the pith likewise goes on 

 without interruption, the older portions collapsing near the 

 centre of the stem as fast as the new tissue is produced by 

 the strips of cambium. That this process cannot continue inde- 

 finitely is self-evident, but as to its limit the author can give 

 no information. In one of the oldest, 1.2 cm thick, stems, 

 investigated by him , the walls of the crushed phloem already 

 formed a mass of cellulose ^'., mm. thick at the centre of the 

 stem. The other portions of the anomalous bast were still 

 young and healthy in appearance, and the thin walls of the 

 cambium-cells would seem to indicate a continued activity on 



