422 
WRIGHT : FOLIAR PERIODICITY 
shrubby plants are all in full bloom. During the dry 
weather many species produce flowers in profusion, but in 
these cases each species seems to have a periodicity unrelated 
to any of those of the surrounding species and usually of very 
limited duration. This is best seen in plants of Bignonia 
Ungui, Pavetta indica, Pancratium species, Bignonia venusta, 
Ruellia tuberosa, and others. 
On the other hand, many liliaceous plants die down in the 
dry weather and the bulbs burst out into new leaf imme¬ 
diately after the arrival of the monsoon rains. Similarly 
with the haulms of the giant bamboo (Dendrocalamus 
giganteus), which begin to elongate in June.* 
Though certain herbaceous plants show a definite period 
of leaf or flower activity, the majority seem to be more or 
less productive during all times of the year, e.g ., Mussenda 
frondosa, and species of Anthurium, Clerodendron, Yinca, 
Panax, Allamanda, &c. 
A case of unusual interest is to be seen in connection with 
the periodicity of species of Strobilanthes, Bl., in Ceylon, 
and I am indebted to Mr. Thomas Farr, Bogawantalawa, for 
much of the information on this subject. Trimen states that 
many of the species are remarkable for their gregarious 
occurrence in vast abundance and over large areas. The 
principal speciesf orm unbroken sheets of undergrowth in the 
forest. They usually live for several years without flowering, 
and though a few flowers may here and there be found 
every year, it is not until the plants have reached a certain 
age, apparently from ten to thirteen years, that the whole 
patch or area bursts simultaneously into blossom. These 
patches or districts are, according to Trimen and Farr, often 
of great extent, and the boundaries between those of different 
ages are very conspicuous, often being as distinct as if arti¬ 
ficially sown. After this general and profuse flowering the 
’Lock, R. H. : On the Growth of Giant Bamboos, with special reference 
> the relation between Conditions of Moisture and the Rate of Growth, 
nnals of the Royal Botanic Gardens, Peradeniya, Vol. II., Part II.. 
