104 Spratt.- — Some Anomalies in Monocotyledonous Roots. 
Cham A ER ops MACROCAR-p a (Palmae). This resembles Monster a 
deliciosa in transverse section, but it has no phloem except that in the ring. 
The cells composing the large mass of the stele are tracheides irregularly 
pitted, and the tracheides of large diameter have multiseriate pits, some of 
which appear to be bordered as in Yucca. 
The results of this research show that a large proportion of Mono- 
cotyledous Natural Orders contain members which have somewhat abnormal 
root structures. The anomaly consists in the filling of the pith of the stele, 
which is rather larger than usual, with scattered vascular elements. These 
are formed by secondary thickening or are differentiated at the growing- 
point, and later in some cases coalesce to form a solid stele. 
Sincere thanks are due to Mr. Hales, Curator of Chelsea Physic 
Gardens, for kindly supplying the material, and to Dr. Ethel R. Spratt for 
supervising the work. 
Summary. 
1. Dracaena roots have two distinct kinds of secondary thickening. 
First, one in which the pericycle becomes meristematic and adds elements 
to the central stele. In large roots this is followed by a second in which 
the pericycle, and finally the cortical layers immediately outside the endo • 
dermis, are meristematic and form vascular bundles like those formed in the 
stem. 
2 . Pandanus and Yucca have internal vascular strands which are 
differentiated at the growing-point in the pith. 
3. In the aerial roots of some of the Araceae, inside the radial ring of 
tracheides, vessels and phloem groups are scattered. 
4. In all these roots the xylem appears to consist largely of pitted 
tracheides. 
Bibliography. 
Caspary : Pringsheim’s Jahrb., i, p. 446. 
A. de Bary : Comparative Anatomy of the Vegetative Organs of the Phanerogams and Ferns, 1884. 
G. Haberlandt : Physiological Plant Anatomy, 1914. 
A. B. Rendle : Classification of Flowering Plants, 1904. 
D. H. Scott and G. Brebner : On the Secondary Tissues in Certain Monocotyledons. Ann. of 
BcCt., vol. vii, No. xxv, 1893. 
E. Strasburger : Text-book of Botany, 1912. 
J. C. Willis : Flowering Plants and Ferns, 1908. 
