41 8 Hill and Freeman . — The Root-Structure 
walls shows signs of disintegration, and their presence may be 
seen in several successive sections. Further, the nuclei of the 
cells originally bounded by these walls are very obvious 
(PI. XIX, Fig. 2; and Text-Fig. 19, 7-12). 
Further back the lumen is again quite clear and contains 
but few nuclei, but still nearer the base of the root a large 
number of nuclei, sometimes as many as twelve in a single 
transverse section, occur at various levels marking the regions 
where the fusion of a number of cells took place. 
The only obvious explanation which will account for the 
foregoing facts is that these central vessels arise very generally 
as single rows of elements, but the initial cells of any one 
vessel may not always be situated immediately one above the 
other to form a continuous string as in many cases, but are 
separated by intervening cells the walls of which ultimately 
break down, and so there is produced a continuous vessel. 
It sometimes happens that these vessels may not reach a great 
length, for although many may be traced through, relatively 
speaking, long distances, some come to an end quite suddenly ; 
this more especially was found to be the case when two had 
been formed quite close together and separated only by the 
common wall. Finally they become lignified in common 
with the other parts, with the exception of the phloem, of the 
vascular cylinder, and possess bordered pits. Whether or not 
this curious development is due to the fact that the roots 
examined were from an abnormally grown plant, cannot be 
decided at present. It is hoped that more material will be 
obtained and the matter investigated further. 
The structures above described are not the only ones which 
are multinucleate, for certain of the inner vessels of the 
metaxylem, which are the first to originate, together with the 
larger sieve-tubes, frequently have as many as four or five 
nuclei at one level 1 . It is doubtful whether these follow the 
1 Since this present paper was written, it has been found that Buscalioni in 
a recent preliminary communication (‘ Sull’ anatomia del cilindro centrale nelle 
radici delle Monocotiledoni,’ Malpighia, 15, 1902) has drawn attention to the 
fact that the mother-cells of the tracheae of the roots of the Dioscoreaceae and 
