ANATOMY OF SOME PLANTS OF A PROVINCE IN IOWA 7 1 
under three systems ol structure. In system i, the photosynthetic tissue is 
itself responsible for the removal of synthetic products from the entire o^gan. 
In system 2, distinct tissues are set apart for photosynthesis and for trans- 
location, the synthetic products being transferred directly from one to the 
other. In the third and most efficient system, the photosynthetic products 
are not transferred directly from photosynthetic elements to the different 
channels but pass first through special intermediary tissues. 
Sachs has shown by experiment that starch is quickly removed from 
specialized parenchyma cells. Haberlandt has observed that the girdle 
type of paHsade shows a very rapid elimination of starch. 
There is apparently diversity of views regarding development of palisade 
parenchyma, some of which Miss Starr (18) in her study of the anatomy 
of dune plants sunimarized as follows: "Mrs. Clements (4) considered 
light the principal factor in the development of deep palisade. . . . Wagner 
reported that Alpine plants exposed to decreased transpiration did not show 
a reduction in palisade, and concluded that not transpiration but assimila- 
tion was mo^e effective in producing that tissue. Pick (14) thought the 
elongated form of the palisade is ancestral, but that for a strong development 
light is necessary; Dufour (5) agreed with him in this respect. Stahl re- 
lated palisade development to light. Eberdt thought increase in palisade 
development is caused by assimilation and transpiration working together, 
and that light in itself is neVer the cause that calls forth palisade parenchyma. 
Vesque and Viet (20) concluded from their experiments that light and dry 
air (accelerating transpiration) result in a greater development of palisade. 
Bonnier (3) adds temperature considerations to these two factors. Kearney 
(9) considers excessive transpiration accountable for both increased palisade 
and succulency. Heinricher related equilateral structure to the vertical 
position of leaves and thought it due to sunny and dry situations, dryness 
being secondary to strong illumination, as some plants growing in damp 
situations have equilateral leaves." 
Solereder (19), who has compiled two comprehensive volumes on the 
systematic anatomy of the dicotyledons in which an enormous amount of 
data has been correlated, substantiates Schimper's views as to the anatom- 
ical indicators of xerophytism, and the reverse, but adds concerning the 
determination of adaptive features that these can be ascertained only by 
(1) examination of individuals of the same species from different habitats; 
(2) experimental treatment under definite conditions differing from, those 
of the natural habitat; (3) the study of a larger group of plants undertaken 
in relation to the geographical area over which its members are distributed ; 
and (4) comparative investigation. In speaking of the enumerated char- 
acters generally associated with xerophytic plants, such as thick cuticle, 
depressed stomata, etc., Solereder says that all these adaptations must not 
be supposed to be quite general, for if that were so, all plants which 
were subject to the same conditions would possess the same biological 
