Tliis, however, is by no means the case with the physiognomy of our own forests, which have for the most 
part lost their original character through our artificial encroachments. We can indeed determine with certainty, 
that their characteristics were produced by the common British Oak, the sessile-fruited Oak, the common 
Beech, the Hornbeam, the Birch, the Alder, the Willow, the Elm, the Scotch Fir and the Austrian black 
Fir, etc., but we are quite unable to state in what proportions these trees were to be met with, as we possess 
no pictorial representations of our primæval forests similar to those in the plates before us. Neither are we able 
to say whether the so-called Pear-tree, the Apple-tree, the Prunus Avium, and other trees which are frequently 
met with in our forests, really belong to our country, or whether they have been brought here and afterwards 
have grown wild, nor do we know where they come from. 
The appearance of our forests changes with nearly every fresh generation of man, and it requires no 
prophetic spirit to be able to foretell that these changes will increase in the same ratio that science succeeds 
in bringing the experience of practicable vegetable physiology into general application. As confirmation of 
this position I will adduce a single example. It is a well known fact that the actual value of a forest is in 
proportion to the amount of carbon it contains. It has further been confirmed that the development of the 
seeds consumes a much larger proportion of carbon than all the other parts of the plant. Mules or mongrels 
which are produced by the crossing of the organs of fructification of two legitimate species, have the remarkable 
and invariable property of forming no seeds, because the pollen which is formed in the anthers of such blossoms, 
does not possess the power of developing its pollen-tubes, which are absolutely necessary to the act of fecundation. 
But the carbon which in legitimate species is employed in the formation of the seeds, can be diverted to the 
formation of the wood in the Mule-species, and this is found to be actually the case, without the slighest injury 
to the wood, in respect either of its durability or of any of the numerous purposes to which it may be applied. 
On the contrary, the microscopical analysis of the wood of bastard-trees, has shown that the membranes of the 
cells are thicker than in the wood of legitimate species from which they were produced ; and this justifies the 
conclusion, that notwithstanding its more rapid growth, the wood of bastard-trees gives promise of a greater 
degree of firmness than we have been accustomed to find in the wood hitherto employed. Bastards bear in 
their habit unmistakeable traces of the characters of the parent plants, but they invariably differ from the latter in 
the much greater rapidity of their growth, as also in their general appearance, and if planted together therefore 
in greater numbers, are calculated to change the physiognomy of the landscape. 
The subject to which I have above alluded is one of great financial importance to every country, and well 
deserves the attention of governments. Should it at some future time be adopted in practice on a larger scale, 
it will conduce very materially to the interest of the state. A very few years are sufficient to enable us to 
recognise the advantages of this procedure, and very few trials are necessary to produce conviction that the 
necessary manipulations are extremely easy and attended with very little trouble. For this purpose I would 
recommend the fecundation of the Scotch Fir {Pinus sylvestris) with the pollen of the Austrian black Fir ( Pinus 
nigricans), of the common British Oak {Quercus pedunculata TV.) with the pollen of the sessile-fruited Oak 
{Quercus Robur TV.), of the common small leaved Elm {Ulmus campestris L.) with the pollen of the Wych-Elm 
{Ulmus montana Smith.) and of the common Alder {Alnus glutinosa) with the pollen of the white Alder {Alnus 
incana.) In the above mentioned examples of Pines, Oaks and Alders, which belong to those plants whose 
blossoms possess separated sexes, it is only necessary, that before the full development of the female organs and 
for a certain period after the fecundation has taken place (which is effected by means of a dry-hair pencil), the 
female blossoms which are used in the crossing, should be carefully enveloped in some cotton texture, admitting 
the access of the air but excluding the pollen of the male blossom of the same plant. The reception of the pollen 
of a different species takes place most readily when the sky is bright and clear, and in the morning hours 
between six and nine. Dull rainy weather is unfavourable even to the normal act of fecundation, but still more 
so to the abnormal process effected by crossing. The stigma which is susceptible of conception exudes either a 
vaporous, or a moist, sticky, sometimes even a fluid juice. This property ceases immediately after the act of 
fecundation has been completed, while in the case of the pollen being entirely excluded, or only indifferent 
dusty matter being sprinkled upon it, the humidity of the stigma continues for a longer period. This stadium 
is the one best calculated for the application of the pollen and thus effecting the crossing. The pollen preserves 
for several days the property it possesses of forming pollen-tubes, as soon as it is brought into connection with 
the slimy fluid secreted on the stigma, and may therefore be collected for this purpose several days before. 
Schoeneberg, near Berlin, 
Fr. Klotzsch. 
