A series of measurements was also made by Heere[904] on _Ramalina reticulata_ (Fig. 64), a rapid growing tree-lichen, and one of the largest American species. The shorter lobes were selected for observation, and were tested during a period of seven months from September to May, five of the months being in the wet season. There was great variation between the different lobes but the average increase during that period was 41 per cent. Krabbe[905] took notes of the colonization of _Cladonia rangiferina_ (Fig. 127) on burnt soil: in ten years the podetia had reached a height of 3 to 5 cm., giving an annual growth of about 3-5 mm. It is not unusual to find specimens in northern latitudes 18 inches long (50 cm.), which, on that computation, must have been 100 to 160 years old; but while increase goes on at the apex of the podetia, there is constant perishing at the base of at least as much as half the added length and these plants would therefore be 200 or 300 years old. Reinke[906] indeed has declared that apical growth in these _Cladina_ species may go on for centuries, given the necessary conditions of good light and undisturbed habitat. Other data as to rate of growth are furnished by Bonnier[907] in the account of his synthetic cultures which developed apothecia only after two to three years. The culture experiments of Darbishire[908] and Tobler[909] with _Cladonia soredia_ are also instructive, the former with synthetic spore- and alga-cultures having obtained a growth of soredia in about seven months; the latter, starting with soredia, had a growth of well-formed squamules in nine months. It has been frequently observed that abundance of moisture facilitates growth, and this is nowhere better exemplified than in crustaceous soil-lichens. Meyer found that on lime-clay soil which had been thrown up from a ditch in autumn, lichens such as _Gyalecta geoica_ were fully developed the following summer. He gives an account also of another soil species, _Verrucaria_ (_Thrombium_) _epigaea_, which attained maturity during the winter half of the year. Stahl[910] tells us that _Thelidium minutulum_, a pyrenocarpous soil-lichen, with a primitive and scanty thallus, was cultivated by him from spore to spore in the space of three months. Such lichens retain more of the characteristics of fungi than do those with a better developed thallus. Rapid colonization by a soil-lichen was also observed in Epping Forest by Paulson[911]. In autumn an extensive growth of _Lecidea uliginosa_ covered as if with a dark stain patches of soil that had been worn bare during the previous spring. The lichen had reached full development and was well fruited.