ON THE IMPREGNATION OF VAUCHERIA SESSILIS, 289 
infinitude of varieties or phases, whose true value can only be 
recognized or determined by the careful observer. In order to 
arrive at a precise knowledge of species and genera, and thereby 
of the generalities of classification, the Lichenological student 
must therefore examine species in all their various states or con- 
ditions,—a work of no little difficulty or discrimination. This 
difficulty is the source doubtless of the present unsatisfactory 
condition of Lichenology ; it is mainly due to the paucity of la- 
bourers in a field where multiplied observation is of paramount 
importance. While however the study of so protean a group is 
an individual labour of forbidding difficulty, it becomes greatly 
facilitated by the division or diffusion of the labour, by the col- 
lection and collation of specimens from different habitats in 
various parts of the world or of the same country or district. It 
is in this form chiefly that we would recommend the subject to 
the attention not only of professed naturalists, but of tourists 
and travellers, as furnishing to them a profitable, as well as a 
pleasing, pursuit in their wanderings, as presenting to them an 
opportunity of contributing towards the elucidation of a hitherto 
neglected branch of the natural history of the Cryptogamia, to- 
wards the gradual filling up of a still conspicuous gap in our 
British Botany. Moreover perhaps the study of no other group 
of plants is so well calculated to lead to the cultivation of habits 
of accurate observation and patient research, than the acquisition 
of which nothing is more important, not only to the observer 
in natural history, but to the educated of all classes of our 
community. 
On the Impregnation of Vaucheria sessilis, DC. By 
W. A. Leieuton. 
Analogous reasoning has long led Botanists to infer the exist- 
ence of sexuality throughout the whole vegetable kingdom. This, 
and the process of impregnation throughout all its stages, have 
been clearly observed in flowering plants. In cryptogamic plants 
however this phenomenon has not been seen, although the exist- 
ence of distinct organs, which have been conjectured to represent 
respectively the male and female organs of impregnation, has 
been long ascertained. These organs have been found to exist 
N.S. VOL. I. 2P 
