384 EIBLIOGRAPITY.
axis, as may be observed in Bartramia Halleriana Hedw. and in many Dicrana.
3. By observing the number of shoots, where several are united together, and form what the author calls a Sympodium. Some mosses produce horizontal subterranean runners, which eventually appear above ground, and produce leaves and fruit. At the point where each runner bends upwards, a bud is deve- loped in the axil of a leaf. This bud forms a second subterranean runner, and at last appears above ground like the former one. This process is repeated yearly, so that by counting the number of shoots which appear above ground, the age of the moss is ar- rived at. Minum unduiatum Hedw., Climacium dendroides W. and M., and Thamnium alopecurum Schpr. may be examined in this way.
4. This method applies to Polytrichum only, and depends upon the fact of the growth of the stem in that genus being carried on through the inflorescence.
5. The 5th method (an uncertain one) is by observation on the size of the leaves. The early spring leaves are the smallest, and those produced as the year advances become gradually larger and larger. "With the following spring the small-sized leaves reappear. Thus each point of commencement of the small-sized leaves marks the commencement of a year. In Leucobryum and in many Dicrana this plan may be used.
In the pleurocarpous mosses, the fruit not being terminal, the growth of the principal axis is not limited, and it is in most cases not possible to fix the age of the stem. An exceptional case exists in Ili/locomium splendens Schpr. where new axes of growth are formed at regular intervals.
The age of moss stems determined in this manner is found to vary between 3 and 10 years, but this does not represent the duration of the whole period of vegetation of a moss. As the moss grows, the older portions of the stem decay by degrees, and in order to determine the length of the whole period of vegetation, it is necessary to examine instances where the decay is arrested. This may be done in the case of Sphagnum where the old portions have formed peat, or where, as sometimes happens, the lower parts of a moss have become incrusted with carbonate of lime.
We have not space to go into the details of the author's re- marks upon this part of the subject, but he arrives at the con- clusion that mosses attain an age equal to that of the oldest trees. Eoze, Ernest, and E. Bescherelle. — Note sur quelques Mousses rares ou nouvelles, recemment trouvees aux moirons de Paris. Bull. Soc. Bot. vii. pp. 433-4.
3. Lichens. Massalongo. — Catagraphia nonnullarum Graphidearum Brasilien-
