Chap. I] CHARACTERS OF THE TROPICAL CLIMATE 239 



are chiefly represented by species of Utricularia. The Scrophulariaceae, 

 however, are only feebly represented. 



Among the Labiatiflorae, the Verbena ceac, to which arboreous as well 

 as shrubby and herbaceous species belong, have a greater importance than 

 the relatively less represented Labiatae. 



The megathermic Campanulinae are limited to the Lobeliaceae, Good- 

 eniaceae, and Cucurbitaceae ; the Campanulaceae are mesothermic, and 

 therefore only appear as mountain plants in the tropics. 



The Rubiaceae, the largest of the three families of the Rubiinae, owing 

 to their great number of species and the important part which many 

 of their representatives play by their frequent occurrence, belong to the 

 most important natural orders in tropical vegetation. The Caprifoliaceae, 

 on the other hand, are extremely scarce in the tropical lowlands, and the 

 Valerianaceae are hardly represented at all. 



The Compositae are about equally important in the tropical and 

 temperate zones ; only a few Liguliflorae are megathermic, but numerous 

 Tubuliflorae, sometimes special groups of them, are megathermic. Most 

 tropical Compositae are herbs, but lianes and small trees also occur among 

 them. The Dipsaceae, which with the Compositae and the small family 

 of Calycereae form the cohort Aggregatac, are chiefly mesothermic, and in 

 the tropics are nearly all mountain plants. 



SELECT LITERATURE. 



1. Climate. 



The general climatic data are chiefly from Hann, Handbuch der Klimatologie. 

 2 Aufl. Stuttgart, 1897. 

 Burgerstein, Alf. Ueber die Transpirationsgrosse von Pflanzen feuchter Tropen- 



gebiete. Berichte der deutschen botanischen Gesellschaft. Bd. XV. 1897. 

 Giltay, E. Vergleichende Studien iiber die Starke der Assimilation in den Tropen 



und im mitteleuropaischen Klima. Pringsheim's Jahrbucher. Bd. XXV. 



1897. 

 Haberlandt, G. I. Ueber die Grosse der Transpiration im feuchten Tropenklima. 



Pringsheim's Jahrbucher. Bd. XXXII. 1897. 

 ■ ■ II. Anatomisch-physiologische Untersuchungen iiber das tropische Laubblatt. 



Sitzungsberichte der Wiener Akademie. Bd. CI, Abth. I. 1892. 

 Johow, Fr. Ueber die Beziehungen einiger Eigenschaften der Laubblatter zu 



den Standortsverhaltnissen. Pringsheim's Jahrbucher. Bd. XV. 1884. 

 Kraus, G. Das Langenwachsthum der Bambusrohre. Annales du jardin botanique 



de Buitenzorg. Vol. XII. 1894. 

 Maxwell, W. The rate of growtli of banana-leaves. Botanisches Centralblatt. 



Bd. LXVII. 1896. 



