112 THE SCOTTISH BOTANICAL REVIEW 



When the embryo fills about half the sac the base of the 

 cotyledon becomes enlarged (text-figure 2, A), but as yet the 

 stem apex cannot be distinguished. Still later a deep cleft 

 appears at the base of the cotyledon (text-figure 2, B), and 

 within this cleft the stem apex (st.) is developed, but its exact 

 position is difficult to determine as it does not project at all. 

 The root remains very short, the cotyledon forming much the 

 greater part of the embryo, in which the second leaf (text- 

 figure 2, B, /.-) is developed before the seed ripens. The 

 sheathing base of the cotyledon quite conceals the stem apex 

 which lies in the narrow cleft between the cotyledon and the 

 second leaf. 



The cotyledon is traversed by a single vascular bundle, but 

 in the oldest specimens examined these had not yet developed 

 any prominent tissue. Whether this is true in the ripe seed 

 was not determined. 



Many of the cells of the embryo contain bundles of needle- 

 shaped crystals such as are so common in the tissues of the 

 older plant. 



An examination of the tissues at the apex of the stem and 

 root showed nothing especially noteworthy. A root cut can 

 be seen, but the separation of the tissue systems at the root 

 apex is not well defined and the stem apex consists of a mass 

 of apparently uniform tissue (text-figure 2, C, D). 



As in most Araceae the basal part of the ovule becomes 

 very massive, so that a section of the seed shows that the 

 embryo-sac occupies with the enclosed embryo only about 

 one-half of the bulk of the seed, the remainder being made 

 up of what perhaps might be termed perisperm, comparable 

 to that in the Piperaceae or Cannaceae, but not developed 

 from the nucellus proper, but from the chalazal region of 

 the ovule. 



Summary. 



1. The flowers of Aglaonema are monoecious ; the pistillate 

 flower consists of a single carpel with a solitary ovule. The 

 inflorescence is decidedly proterogynous. 



2. The nucellus is relatively small and only the upper 

 portion of the integuments is free, the basal part being 

 merged with the much enlarged chalazal part of the ovule. 



