68 BOTANICAL GAZETTE [July 



into the radial, it is clear that these various conditions are all 

 modifications of the radial arrangement (fig. 3). In most cases 

 the amphivasal condition is not attained. This occurs where 

 the xylem grows around only one end of the band of phloem, 

 giving a crescent-shaped xylem (fig. 9). This arrangement may 

 be either an intermediate condition between the parallel bands and 

 the amphivasal situation, or it may represent the final develop- 

 ment at that point and, breaking up, return to the parallel-banded 

 type without the formation of the amphivasal. These modifica- 

 tions seem to be entirely confined to the strobilus cylinder. In 

 the vegetative stems and in the vegetative part of the stem which 

 bears the strobilus, there is no evidence of the modifications of the 

 stele which are so characteristic of the strobilus. All vegetative 

 parts are radial as to their stelar structure excepting where this 

 condition is modified by branching. 



At the base of the vegetative stems roots leave the stele, and 

 pass downward through the cortex for some distance before finally 

 passing out of the stem. These roots show a peculiar tendency to 

 form a ring of xylem resembling the ring of xylem in the stem. 



L. Phlegmaria and L- varium 



Both these species greatly resemble L. carinatum in the tendency 

 of the strobilus to develop the parallel-banded type of stele, by 

 the peripheral growth of protoxylem and by the development of 



metaxylem 



— — _ j 7 ._ ^ 



oem. This tendency to the peripheral 



lem is esoeciallv marked 



in the mature stem it is sufficiently extensive to inclose one-third 

 to one-half of the stele in certain portions for a considerable distance 

 (fig. 15). L. Phlegmaria shows many crescent-shaped masses of 



m 



dom 



\ o / :tv 7 -j 1 



if ever fully attains the amphivasal condition reached by 

 L. carinatum. The parallel-banded type in L. varium is not always 



from the radial arrangement 



natum. 



methods 



of the stele. One is the radial as described for L. carinatum (figs- 

 10, n). The other is the method in which the radial arrangement 



