102 
J. C. Th. Uphof, 
of Asia and Australia. As outstanding localities may be considered 
rocky and sandy situations in the midst of a non-xerophytic flora ; 
such as dry ridges and rock outcrops occurring near mesophytic 
forests, and sand barrens which may occur anywhere. 
Although excellent work has been published on the anatomy 
and morphology of Selaginella, especially by Cornaille (4), 
Gibson (9, 10), Haberlandt (12), Mitchell (17), Seyd (21), and 
Treub (24), only Leclerc du Sahlon (14) in 1889 and Wojinorvid (29) 
in 1890 have contributed toward the knowledge of the xerophytic 
S. lepidophylla , Spring. Since that time, very little has been done 
on the subject, and other xerophytic species have scarcely been 
studied from an anatomical and physiological standpoint; com¬ 
parative studies with plants of the same species under different 
environment have never been undertaken, neither hasa physiological- 
anatomical classification of the plants in question been made. 
Comparing various species of xerophytic and hygrophytic 
Selaginellas one soon notices the very close proximity of the dorsal 
and ventral leaves in the former (Fig. I, 1, 4, 5, 6), and the distance 
between the succeeding leaves in most species of the latter (Fig. 
I, 3). Moreover there is a striking similarity in the size of leaves 
in all xerophytic species the author has worked with ; the size of 
the dorsal leaves differs only very little from that of the ventral 
leaves, although they may have slightly different shapes (Fig. II, 
1, 2, X, 1, 2). In all hygrophytic Selaginellas, on the other hand, 
the difference in size and shape of dorsal and ventral leaves is very 
marked (Fig. I, 3). The writer considers the similarity in size in 
leaves of the xerophytic species (Fig. I, 1, 4, 5, 6; II, 1, 2, 8, 9; X, 
1, 2) to be of much importance from a photosynthetic standpoint, 
as will be shown later: under the influence of their extreme 
environment the ventral leaves contain but few chloroplasts. Most 
of the production of organic matter therefore, as far as the action 
of the light is concerned, has to take place in the green cells of the 
dorsal leaves ; were these leaves several times smaller, as is the 
case with hygrophytic ones, an insufficient amount of organic food 
would be formed, threatening perhaps the existence of the species. 
It is suggested that this factor must have been effective at the 
time, hundreds of centuries ago, when xerophytic species of the 
type S. lepidophylla , originated from distinct heterophyllous 
hygrophytic or semi-hygrophytic forms; those adapted to arid or 
semi-arid situations being alone able to survive. 
