In CLEOME AND IsoMERIS. 245 
cells retain their living contents even after lignification of the 
cell membrane is completed. 
In the mature ovule this tissue extends upwards to a point just 
above the apex of the nucellus, where it merges, somewhat 
abruptly, into the enveloping layer of aqueous cells. For a 
Fic. 2.—A later stage in the development of the lignified tissue in the inner 
integument of the ovule of Cleome spinosa. 
time there is apparently no change in the amount of lignified 
tissue produced, but the ovule itself increases considerably 
in bulk. 
What particular function these elements serve at this period 
in the development of the ovule is a matter for speculation. The 
presence of this specialised tissue round the micropyle certainly 
ensures that the pore will be preserved, but at the same time 
this pronounced metamorphosis of the apical cone of the inner 
