PDF - CES (IISc)

GROWTH AND DURATION 255
in the same direction, and the plant increased 175 cm. in one year. Two
other plants, deprived of their lobes, regenerated and increased from 2 and
5 cm. respectively to 3^5 and 6 cm. No other measurements are quite so
high as these, though a plant of Parmelia caperata (sterile), measuring from
I to 2 cm. across, reached in eight years a dimension of 10 by 13 cm. Other
plants of the same species gave much slower rates of increase. A section of
railing was marked bearing minute scattered squamules of Cladonia pityrea.
After two years the squamules had attained normal size and podetia were
formed 2 to 4 mm. long.
Several areas of Verrucaria muralis were marked and after ten months
were again measured; the largest plants, measuring 2*12 by 2^4 cm. across,
had somewhat altered in dimensions and gave the measurements 2'2 by
3 cm. Some crustose species became established and produced thalli and
apothecia in two to eight years. Foliose lichens increased in diameter from
'3 to 3'5 cm - Per year - So far as external appearance goes, apothecia are
produced in one to eight years; it is concluded that they require four to
eight years to attain maturity in their natural habitats.
B. SEASON OF FRUIT FORMATION
The presence of apothecia (or perithecia) in lichens does not always
imply the presence of spores. In many instances they are barren, the spores
having been scattered or not yet matured the disc in these cases is ;
composed
of paraphyses only, with possible traces of asci.
however, some lichens may be found in fruit.
In any month of the year,
Baur 1
found, for instance, that Parmelia acetabulum developed carpogonia
the whole year round, though somewhat more abundantly in spring and
autumn. Pertusaria communis similarly has a maximum period of fruit-
formation at these two seasons. This is probably true of tree-lichens
generally: in summer the shade of the foliage would inhibit the formation
of fruits, as would the extreme cold of winter ; but were these conditions
relaxed spore-bearing fruits might be expected at any season though perhaps
not continuously on the same specimen.
An exception has been noted by Baur in Pyrenula nitida, a crustaceous
tree Pyrenolichen. He found carpogonia only in February and April, and
the perithecia matured in a few weeks, presumably at a date before the trees
were in full leaf; but even specimens of Pyrenula are not unusual in full
spore-bearing conditions in the autumn of the year.
To arrive at any true knowledge as to the date and duration of spore
production, it would be necessary to keep under observation a series of one
species, examining them microscopically at intervals of a few weeks or months
1 Baur 1901.