4 INANITION AND MALNUTRITION 



associated with the occurrence of particular modes of reproduction in Algae and 

 Fungi." 



DeVries ('oo) noted that the extent to which the stamens are metamorphosed 

 into carpels in Papaver somniferum polycephalum is a highly variable character, 

 and is determined by external (especially nutritional) factors at a certain critical 

 period, about the seventh week of development. Influences at earlier or later 

 periods are ineffective. This may perhaps explain some of the conflicting results 

 which have been obtained in other forms. 



There is also clearly a difference between the monecious and diecious 

 forms, in respect to their susceptibility to sex-modification by environmental 

 changes, as has been emphasized by Strassburger ('oo) and O. Schultze 

 ('03), who concluded that the sex (in diecious forms) is predetermined 

 in the ovum, and apparently unmodified by environmental changes. 

 Thus Strassburger could obtain no modification of sex in Melandrium. Noll, 

 while getting positive results in the usually monecious Equisetum Telmateja 

 (only male prothallia developing in cultures without phosphates), had negative 

 results with the diecious Marchantia polymorpha. 



Coulter, Barnes and Cowles ('11) cited numerous examples of the reproduc- 

 tive process as influenced by various unfavorable conditions, including dessica- 

 tion and decreased food supply. The effects vary greatly in different species. 

 In moulds generally the formation of asexual spores is favored by dessication 

 and starvation (and of zygospores by the opposite conditions), but the sexual 

 mode of reproduction is induced by food scarcity in Saprolegnia. According to 

 Morini ('85), a reduction of nutrition appears necessary for zygosporulation in 

 the Ustilagineae. As to sex determination, Coulter, Barnes and Cowles stated 

 that in diecious plants undernourishment and xerophytic (dry) conditions 

 apparently facititate the development of male (staminate) plants, but other 

 factors must be considered. Recent evidence indicates that in diecious plants, 

 as in animals, sex is determined at a much earlier period than was formerly 

 supposed, being usually predetermined in the gametes, independently of external 

 factors. Apparent change of sex seems best explained by assuming that such 

 forms are at least potentially bisexual, and that external factors may either 

 cause suppression of one of the sexes (as in Zea) or stimulate development of the 

 sex commonly suppressed (in Carica). 



Love ('09) found that in peas a decrease in the food supply decreases the 

 coefficient of variability in yield and number of internodes, but increases the 

 variability in height. 



Data upon the cytological effects of starvation in plants appear relatively 

 few, and have been described chiefly in connection with various forms of partial 

 inanition (to be considered later). Cunningham ('80) found protoplasmic 

 atrophy and fatty degeneration in the mycelium and fruiting organs of certain 

 moulds (Choanephora and Pilobolus crystallinus) kept in distilled water. Bok- 

 orny ('92) likewise found cytoplasmic atrophy, as well as changes in fat content, 

 cell-sap, etc. of Spirogyra cells (see also later under potassium deficiency). 

 Kosinski ('02) found in fungus cells {Aspergillus niger) during starvation dim- 

 inished respiration and a gradual consumption of the plastic formed material to 



