372 M or pho genetic Factors 



Lyon and Garcia (1944) studied the effects of anions and cations on 

 stem anatomy of tomato plants in over 40 nutrient solutions varying in 

 the relative proportion of nitrogen, sulfur, and phosphorus, and of calcium, 

 potassium, and magnesium. Differences in stem diameter and in relative 

 amounts of phloem, xylem, and pith, as well as cellular differences in 

 parenchyma of pith and cortex, vessels, fibers, phloem cells, and pericycle 

 fibers, were correlated with specific differences in the nutrients. 



Makarova ( 1943 ) examined the relation of various nutrient elements 

 to traits described by Maximov as xeromorphic and found that, in gen- 

 eral, such traits were intensified by phosphorus, boron, and manganese 

 and diminished by potassium and iron. These effects chiefly concern cell 

 size. 



MORE COMPLEX SUBSTANCES 



Sucrose itself may have certain morphogenetic effects. Yates and Curtis 

 ( 1949 ) found that the root-shoot ratio in orchid seedlings growing in 

 nutrient media is not related to the C/N ratio, as in so many cases, but to 

 the concentration of sucrose alone, the optimum concentration for root 

 growth being markedly higher than for shoot growth. At the best con- 

 centration for root growth, shoot growth was reduced. 



In sporelings of Marsilea grown with varying concentrations of glu- 

 cose, Allsopp ( 1954 ) observed that in low concentrations the plants 

 showed many of the traits of the water forms of amphibious plants, and 

 those at higher concentrations resembled land forms. This presumably 

 is not owing, however, to the specific morphogenetic effect of glucose 

 but to the fact that in the lower concentrations water is more available 

 osmotically and conditions therefore to some extent simulate aquatic 

 ones (p. 332). 



By using glycogen, soluble starch, or dextrin as a carbon source in- 

 stead of sugar, Nickerson and Mankowski (1953) were able to convert 

 the normal budding yeast type, in Candida albicans, to a filamentous 

 mycelial type. 



Sossountzov (1954) tried various amino acids instead of inorganic 

 nitrogen as nitrogen sources in the culture of fern prothallia and found 

 that under these conditions they tended to be atypical but that in most 

 cases the proportion of filamentous prothallia to cordate ones was con- 

 siderably increased. 



Hammett and Walp (1943) studied 10,000 fertilized Fucus eggs, half 

 of which were exposed to proline and half were not, and observed that 

 proline increased differentiation here (as measured by the production 

 and growth of rhizoids) much as it has been shown to do in ani- 

 mals. Barghoorn (1942), however, found no definite evidence that pro- 



