448 MORPHOLOGY OF THE ANGIOSPERMS 



described as borne "opposite the median trace" of the carpel. They 

 seem to represent survivors of submarginal placentation, though de- 

 scribed under the peltate theory of carpel form as "laminar." The ovule 

 has a strong vascular trace, which branches freely in the chalaza and 

 enters the outer integument. Differentiation of funicle, raphe, and in- 

 teguments is difficult in most taxa and is often complicated by adnation 

 of the ovule to the ovary wall; the adnate condition is the basis for the 

 description "ovule sessile." The integuments show various degrees of 

 fusion; often they are distinct only near tlie micropyle. Attalea is de- 

 scribed as having two integuments; Phoenix, only one. 



The Pollen and Pollination. The pollen grains are of various sulcate 

 types and most resemble those of the Cyclanthaceae, Liliaceae, and 

 Amaryllidaceae. Pollination is by various agents, perhaps chiefly by 

 wind, but also by insects — wasps, in part, in Cocos. It has been re- 

 ported as by birds in Eupritchordia. Pollination seems to be in transi- 

 tion from entomophilous to anemophilous, as in Salix and Acer, accom- 

 panying development of unisexuality. Pollination by beetles should be 

 looked for in the primitive genera. 



The Fruit 



The fruits vary in type but are mostly drupaceous, ranging to non- 

 fleshy types. In Nipa, the closely aggregated fruits form a syncarpium. 



Discussion 



The palms are primitive monocotyledons that have progressed far in 

 specialization in various characters. Habit, leaves, inflorescences, flowers, 

 pollination, fruits, all give evidence, in their diversity of form, of a long 

 period of evolutionary modification. Variety in habit is great. Whatever 

 the interpretation of the evolutionary history of the unbranched tree, 

 the range of form from rhizomatous "herbs" to shrubs, woody vines, 

 and tall trees is remarkable for a single family. 



The history of leaf form in the palms is probably unique in angio- 

 sperms (see Chap. 1). The derivation of the compound leaf from the 

 simple — doubtless an evolutionary story in other families also — is, in 

 this family, by dissection of a type probably not present in other 

 angiosperms. The remarkable ontogeny of the compound leaf of the 

 palms sets the palms well apart from other angiosperms. The compound 

 leaf must have arisen early in the history of the angiosperms and inde- 

 pendently in the palms. The primitive palm leaf was, doubtless, simple, 

 with pinnately parallel venation. 



The history of leaf modification alone is sufficient evidence that the 

 palms are a very old family. Fossil leaves support this record. Pro- 



