60 
ANNALS OF THE 
ABSTRACT OF RECENT DISCOVERIES IN BOTANY, AND THE CHEMISTRY 
OF PLANTS. 
Bt Professor George Lawson, Pn D. 
Venation of Mosses. — In Botany the term venation has reference to the dis- 
tribution of the so called veins or nerves of the leaf. These veins or nerves have 
nothing in common with the apparatus to which those terms arc applied in the ani- 
mal kingdom ; they form merely the framework upon which the cellular expansion 
of the leaf is, so to speak, stretched out ; but they are in some cases important to 
the systematic botanist, as indicating the structural grade of plants. In mosses, the 
existence of a central leaf rib has been long recognized. In some cases this is ab- 
sent. In others there is in addition a thickening of the leaf-margin. Mr. G. Gul- 
liver, F. R. S., has published a paper in the Annals of Natural History (ser. 3, vol. 
v., p. 298), in which he suggests that these thickened margins are in reality 
marginal nerves or ribs. This is a very important suggestion, and may 
lead to useful results in reference to the morphology of the moss leaf That 
in many cases the marginal thickenings of moss leaves structurally resemble, 
in every respect, the midribs, is a fact that cannot have escaped the attention of 
Muscologists, especially in such species as Atrichum undulatum, yet Mr. Gulliver is 
the first to suggest v/hat seems to be their true nature. The details he gives are 
very meagre; it is to be hoped that he will follow out the subject, and, by a care- 
ful study of the details of leaf structure in the various families of mosses, deduce 
some general results that will lead to a recognition of his views by the describers 
of these interesting and beautiful plants. There are many points on which Bryol- 
ogists have not yet agreed, and one of the most necessary, so far as regards descrip- 
tive Muscology, is to dctcrmir.e what is to be regarded as midrib and what as 
lamina. The new point of view will no doubt revive the discussion of such ques- 
tions, with profit. 
