338 
Campbell. — Studies on the Araceae, III. 
The Ovule. 
In the youngest available ovules the integuments were already com- 
pletely formed and the archesporium could be recognized. At this stage 
the ovule closely resembles that of Aglaonema , and its further history 
recalls in many ways that of A. commutatum. 
The young ovule is very massive, but this is mainly due to the great 
development of the base of the ovule and the integuments, as the nucellus 
is relatively small and slender. The apex of the nucellus is flattened and 
is on a level with the top of the two integuments which are at this time 
of equal length (PL XVI, Fig. 38). 
Occupying the axis of the nucellus in the youngest ovules found, were 
two superimposed cells with large and conspicuous nuclei. These were 
probably sister-cells, but the actual division of a primary archesporial cell 
was not seen. 
In the other ovules of about the same age the two sporogenous cells 
were side by side, and in some others there was a more or less irregular 
group of what might be interpreted as sporogenous cells (Fig. 40). The 
position of these was sometimes such as to make it probable that they were 
not derived from the division of a common mother-cell, but may have been 
the product of two or three independent hypodermal cells — in this respect 
showing a resemblance to Arisaema 1 where the archesporium-cells show, 
in some cases at least, a similar independent origin. 
The cells of the nucellus-apex generally divide by periclinal walls, but 
some of them may remain undivided. Evidences of the formation of 
a tapetal cell cut off from the archesporium were seen, but whether this is 
regularly the case is doubtful, and it seems quite as likely that no tapetum 
is developed in most cases. 
The further history of the sporogenous cells shows extraordinary 
variation, and in most cases examined the number of embryo-sacs which 
begin to develop is more than one. In some instances several sacs develop 
about equally for some time. So variable, indeed, does Nephthytis show 
itself to be, that it is quite impossible to determine what may be called the 
normal method of development. 
As development proceeds the mass of sporogenous tissue becomes very 
conspicuous and gradually encroaches upon the lateral nucellar tissue. The 
number of sporogenous cells is variable, and it is impossible to determine 
just how many are to be looked upon as primary embryo-sacs. 
The ovule shown in Fig. 41 was probably abnormal, but it illustrates 
the remarkable development of sporogenous tissue which may take place 
before a definite embryo-sac is recognizable. In this case the division-walls 
1 Campbell, loc. cit., II, p. 667. Mottier, Bot. Gazette, 1892. 
