THE GENOTYPICAL RESPONSE OF THE PLANT 
215 
the Hieracium tables (placed at the end of the chapter) for the length 
and width of the middle leaves are average values based upon the 
measurements of five leaves of each plant. The values given in the 
same tables of the magnitude of the angles formed by the stem with 
the perpendicular refer to the angles of the largest stem of the indi- 
vidual. These values have by tests been found to deviate + 5 degrees 
from the correct value. Field numbers preceded by one or more 0 
indicate that a corresponding number of individuals have died and left 
gaps in the row. It has been found practical to use this method in 
checking the individuals. A — in the table columns indicates that 
measurements or notes have not been taken because of the wilted con- 
ditions of the leaves or of the whole plant (or because of damage by 
rabbits in some cases). 
The cross-sections made of different leaves have for technical rea- 
sons been collected at the end of the Hieracium chapter. 
The terminology followed in discussing the distribution of various 
shore species in the different zones of the shore is that worked out by 
SERNANDER (1917). 
In arranging the material it has been thought best to group it 
under seven headings, the first four containing the results of the cul- 
tivations of shade forms, dwarfs, succulent shore forms of inland spe- 
cies, and halophytes, and the last three containing the data for inland 
and coast forms of Sedum maximum, Armeria vulgaris and Hieractum 
umbellatum respectively. The general discussion of the results and the 
_ bearing upon the problem which these results imply will then follow. 
1. MATERIAL AND CULTURES OF SHADE FORMS OF 
MESOPHY TIC SPECIES. 
A great number of mesophytes are known to develop shade forms in 
response to subdued light, and the morphological and anatomical changes 
brought about in such forms, especially in the leaves, are well known. 
The further question, whether or not all shade forms occurring in nature 
are shade-modified open air plants, or whether hereditary shade varie- 
ties also exist within certain species, has received but little attention. 
The cultures made in order to settle this point cannot yet be said to 
be conclusive, since no crossings have been made, but they are cal- 
culated to throw some light on the problem. The plants employed 
are Lysimachia vulgaris L., L. nummularia L. and Dactylis glomerata L. 
