380 MORPHOLOGY OF THE ANGIOSPERMS 



sometimes applied to fruits with two or more carpels — Compositae, 

 Typhaceae — or with two seeds. No morphological line separates an 

 achene from a nut, though the nut is typically syncarpous. The syn- 

 carpous structure of most nuts is obscure in the mature fruit, and 

 errors of interpretation of carpel structure of nuts have been made. The 

 fruit of Conjhis has been described as monocarpellate, but is clearly 

 bicarpellate, with one ovule in each locule. Morphologically, achenes 

 consist of a seed with an enclosing ovary wall. The seed coats may be 

 free from, or adnate to, the ovary wall. They may be reduced to a thin, 

 papery layer or be represented by mere vestiges of tissue. Where there 

 is intimate adnation, the two structures may be distinguishable only by 

 ontogenetic studies. 



Fruits may consist of seeds without an ovary wall; the seeds may 

 ripen "naked" — Catdophyllum, Lotirya, some parasites. (The naked 

 seeds of certain parasites — Sarcopodales — have been considered to 

 be primitively naked, and the taxon, therefore, not to be angio- 

 spermous. This interpretation provided part of the basis for the estab- 

 lishment of a taxon, the Prephanerogamae, intermediate between the 

 gymnosperms and angiosperms. ) In CaulophyUum, the developing fer- 

 tilized ovules soon break through the ovary wall, which ceases to 

 grow, and the ovule matures like a fruit. 



Correlation has been seen between advanced characters — fruits of the 

 achene or nut type — and anemophily. Some correlation has been seen 

 between habit and fruit type. Trees, shrubs, and climbing herbs tend 

 to have large and fleshy fruits; terrestrial herbs nearly always have 

 small, dry fruits. 



As interpreted under the durian theory, the primitive fruit is a fleshy 

 follicle or cupule, with numerous arillate seeds. But arils are present in 

 widely scattered taxa and seem to represent ecological adaptations in 

 dissemination. The evidence from broad comparative studies through- 

 out the angiosperms supports the view that the follicle with many seeds 

 is the primitive fruit. 



BIBLIOGRAPHY 



The Seed 



Artschwager, E.: Development of flowers and seed in the sugar beet. Jour. Agr. 



Res., 34: 1-25, 1927. 

 , E. W. Brandes, and R. C. Starrett: Development of the flovi^er and seed of 



some varieties of sugar cane, ]oitr. Agr. Res., 39: 1—30, 1929. 

 Billings, F. H.: Beitriige zur Kenntnis der Samenentwicklung, Flora, 88: 253—318, 



1901. 

 Brandza, M.: Developpement des teguments de la graine. Rev. Gen. Bat., 3: 1-32, 



71-96, 105-126, 150-165, 229-240, 1891. 

 Brink, R. A., and D. C. Cooper: The endosperm in seed development, Bot. Rev., 



13: 423-541, 1947. 



