THE GENOTYPICAL RESPONSE OF THE PLANT 239 
forms, dwarf forms, forms presumably adapted to live on sandy 
shores, on rocky shores, on sea-weed banks, etc. have been distingui- 
shed within several species and named by systematists. The poly- 
morphism has also been assumed to be due, to a certain degree, to the 
vecurrence of hybrids between some of the species. The method largely 
employed in my own work has been to collect series of young plants 
of the various ferms and species from different points on the Swedish 
coast for my cultures. As many as possible of these transplanted in- 
dividuals have then been isolated with pergamin bags at the stage of flow- 
ering, and the offspring has been compared with the mother-plants. 
All the species investigated seed perfectly well when isolated in that 
way. The isolations have been continued for several years and a con- 
siderable number of biotypes have been isolated from the different 
species. A remarkable multitude of different hereditary forms have 
thus been found to build up the species in nature. The frequent self- 
fertilization, occurring also in nature, tends to preserve these different 
forms, thus giving rise to the perplexing polymorphism found. That 
this polymorphism is sometimes increased by crossings between dif- 
ferent species, and by the direct influence of environmental factors 
upon the plants will also be shown. It has been thought best to dis- 
cuss the different species separately. 
A. ATRIPLEX LITORALE. 
The species occurs commonly along the Swedish coast. It has a 
shallow root-system and is therefore limited to the lower portion of 
the beach, where it often roots in the sea-weed banks thrown up. 
Farther up on the sandy beach only dwarfed forms are produced. 
The plant flourishes best in sheltered places and keeps away from the 
most exposed localities (cf. also TurEsson 1919 a). It reaches its best 
development along the Sound, especially on the beach-lines borde- 
ring the bays and coves, where masses of Fucus and Zostera have 
collected. The dimensions reached by the plant along the Sound are 
not attained on the coast farther to the north, e. g. in Halland and in 
Bohuslan. The forms met with in sheltered places along the Sound 
are often tall, erect, and very robust, while the forms farther up on 
the more exposed west coast are lower of stature and more spreading. 
The question arose whether these differences between the forms of 
the Sound and those of the coast line to the north are hereditary or 
only modificatory and wholly due to differences in the environment. In 
