102 Sprat t . — Some Anomalies in Monocotyledonous Roots. 
The roots of Dracaena Draco become larger than those of the other 
two species examined. This increase of size no doubt accounts for the fact 
that this species in the older roots shows a second type of anomalous 
secondary thickening in addition to that already described. This second 
type recalls the anomalous thickening of Dracaena stem. A cambium is 
formed just outside the endodermis, and this forms vascular bundles con- 
sisting of a few phloem elements surrounded by tracheides (see PI. Ill, 
Fig. 4). The latter are pitted like those in the central root stele, but they 
are shorter and wider (see PI. Ill, Fig. 6 ). 
Dracaena Draco , in fact, is one of the species which exhibit the type 
of secondary thickening similar to that found in the stem and which so 
many writers have described. The roots at my disposal were quite small, 
not exceeding half an inch in diameter, and in view of Scott and Brebner’s 
paper it is interesting that in them this secondary thickening was taking 
place outside the endodermis, not in the pericycle. Previous writers for the 
most part make no remarks upon the anatomy of the central stele, but 
according to this research there is another secondary growth which takes 
place earlier and even in the small roots. Several species of Dracaena 
which do not develop very large roots never undergo this extra-stelar 
secondary thickening. 
Pandanus has been put by A. de Bary with Dracaena , as mentioned 
above. Stilt roots were examined, and in transverse section show a large 
vascular cylinder with xylem and phloem groups arranged radially round 
the periphery. The centre has a parenchymatous groundwork, but is 
largely occupied by groups consisting of pitted tracheides, parenchyma, and 
phloem, and containing intercellular spaces of large diameter. There are 
also groups of fibres scattered about ; these also appear in the cortex. All 
the elements found in the stele are differentiated at the growing-point. In 
transverse section near the tip there are no thickened cells except the 
scattered groups of fibres mentioned, but otherwise it resembles the stele in 
the older root. Thus Pandanus resembles Dracaena in having xylem and 
phloem elements internal to the vascular cylinder, but shows no secondary 
thickening. It has an extensive development of the calyptrogen, giving rise 
to a many-layered root-cap which is successively split off in flakes. 
yucca filamentosa resembles Pandanus in that it has internal 
strands differentiated at the growing-point, but these consist of large and 
small tracheides as in Dracaena. There is no internal phloem. The 
tracheides possess two rows of pits which, although distinct from those of 
Gymnosperms, appear to be bordered like they are (see PI. Ill, Fig. 13). 
Monster A deliciosa (Araceae). The stele of the aerial roots of 
this plant shows a peripheral ring of xylem and phloem arranged radially. 
Inside this, it consists of tracheides with simple pits irregularly distributed. 
Scattered through these there are : (1) xylem vessels with multiseriate 
