Some Anomalies in Monocotyledonous Roots. 
BY 
AMY VERA SPRATT, B.Sc. Hons. (LomL). 
University Scholar , King's College , London . 
With Plate III and one Figure in the Text. 
“7 the end of the last century a good deal of controversial discussion 
A about secondary thickening in Dracaena root took place amongst the 
botanists of the day, and it became fairly established that secondary growth 
similar to that found in the stem occurs in the larger roots. Caspary in 1858 
states that the pericycle becomes meristematic, and this is confirmed by 
A. de Bary, who states that ‘ the pericambium assumes the properties and 
function of extra-fascicular cambium In contradiction to these two 
authorities Strasburger names the cortical cells abutting on the endodermis 
as the origin of the cambium. Scott and Brebner in 1893 reconciled these 
two accounts by showing that there are three different conditions of 
secondary growth : (1) a cambium appears in the pericycle, (2) a cambium 
appears in the cortex just outside the endodermis, (3) the pericyclic cambium 
is succeeded by an extra-stelar cambium. These three appear in different 
regions of the same root. 
Although there has been so much discussion with regard to the 
secondary thickening which takes place outside the stele, very little 
attention has been paid to the central stele itself. A. de Bary apparently 
examined roots of terrestrial Aroideae, Pandaneae, and Dracaena . 
His description is somewhat involved, but he says that in the Aroideae 
the stele consists of a sclerenchymatous cylinder in which wide vessels 
and sieve tubes are distributed, not lying in radial rows. Pandaneae 
and Dracaena , according to him, exhibit essentially the same structure, 
except that the sclerenchymatous cylinder is not homogeneous but consists 
partly of parenchyma. He further adds that in the Pandaneae and 
Dracaena the pith is traversed by sclerenchymatous strands enclosing either 
vessels or sieve tubes. This, according to A. de Bary, is the primary 
structure which Dracaena roots retain unaltered when secondary thickening 
as above described occurs. Haberlandt mentions that the root structure of 
the aerial roots of many epiphytic Aroids, the ordinary roots of certain 
Palms, and the stilt-roots of Pandanns is anomalous. He says that the 
[Annals of Botany, Vol. XXXIV. No. CXXXIII. January, 1920.] 
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