582 Annals New York Academy of Sciences 



The Usefulness of ike Microscopical Evaluation of Morphological Criteria 



Organisms consist of highly organized organic mailer. Consequently, 

 they have a characteristic and speciiic chemical composition which reveals 

 itself in specific morphology. Most morphological features serve the specific 

 life functions of the organisms. 



Morphological features develop through 2 basic processes: hereditary proc- 

 esses transmitted through genes from parent to offspring, and environmental 

 influences affecting the individual. The first process results in genotypical 

 morphological features; the second leads to phenotypical morphologies. Geno- 

 typical features are constant within a narrow limit (Dobshansky, 1951), 

 whereas the phenotypical features are apt to show wide variations. Identifi- 

 cations based upon morphology must be restricted to genotypical features 

 (Cholnoky, 1960). This means, of course, that a particular species cannot be 

 identified through the examination of a single individual. A series of specimens 

 must be examined to define the limits of phenotypical variation. The geno- 

 typical and the phenotypical morphological features are functional. However, 

 genotypical morphology reflects hereditary needs (phylogenetic adaptation), 

 whereas phenotypical features represent individual needs bearing on environ- 

 ment (ontogenetic adaptation; Goldschmidt, 1940). 



The relationship between function and morphology is apparent among 

 plants of higher and lower orders. For example, two species of the flowering 

 plant genus Ambrosia, A. elatior and A. artemisiaefoUa, live in habitats which 

 are exposed to different degrees of sunshine and contain different amounts of 

 moisture. The latter species, A . artemisiaefoUa, lives in a semidesert environ- 

 ment. Consequently, the size of the foliage is smaller than that of the former 

 species, A. elatior, and scleral elements are abundant in the leaves to provide 

 mechanical support during periods of severe loss of turgor. 



The Ambrosia pollen, i.e., ragweed pollen, shows a characteristic genotypical 

 morphology, a solid, spinose exo-exine. Clearly, the spines represent a geno- 

 typical feature because they must develop from the tapetal layer of the pollen 

 sack. The pollen grains, during their ontogenesis, are not directly exposed to 

 environmental influences. The spines are formed by apposition. For the 

 same reason the spines of the ragweed pollen are solid rather than hollow. 

 The solid intine can be penetrated by 3 pores only. The spines may facilitate 

 the transportation of the pollen grains. The characteristic tricolpate structure 

 is always observable upon proper focusing of the microscope (Erdtman, 

 1952, 1957; Faegri and Iversen, 1950; Jonas, 1952; Hyde and Adams, 1958). 

 See FIGURE 1, pollen grain of Ambrosia trijida; figure 2 the same in optical 

 section; figure 3, Hystrichosphaeridium sp. from the Upper Cambrian; fig- 

 ure 4, pollen grain of Dahlia pinnata; figure 5, Hystrichosphaeridium from 

 the Upper Cambrian. (Figures 1, 2, and 4 were taken from Wodehouse, 

 1942, and correspond to his numbers; 118, 119, and 115, respectively; figures 

 3 and 5 were taken from Timofeev, 1956, and correspond to his numbers 20 

 and 19, respectively.) 



There are similar looking species of unicellular, aquatic plants. For ex- 

 ample, Hystrichosphaeridium Deflandre is covered with spines. These spines, 

 however, serve a different function, develop through different embryological 



