——— = - 
27 
be of equal or even of greater importance. The leaf has no 
stomata or breathing pores and consists generally of only one layer 
of cells, which are not all of the same size and shape, for those at the 
base are often much larger than those at the apex. Not only is 
the size of the cells noteworthy but also their shape, as this is found 
to be highly characteristic in whole families of Mosses. In many 
cases, the leaf is furnished with a vein, which is sometimes narrow 
and sometimes broad—in some cases it ends as a point to the leaf, 
while, in others, it is much prolonged into an excurrent point or 
hair, as in Tortula. Ina rare case or two, it leaves the leaf much 
below the tip and so resembles the dorsal awn, so common in grasses 
Those bodies called stipules which are so noticeable in many 
families of flowering plants, do not occur in mosses, but they are 
found in many of the Hepatic. Chlorophyll, the green colouring 
matter of plants generally, is more or less abundant in mosses, in 
the protonema as well as in the leaves, the terms “highly 
chlorophyllose ” and ‘‘ sparingly chlorophyllose”’ being much used 
in descriptions. It is now time for us to look at one of these 
specimens (let us take the Polytrichum commune or common 
hair-moss) and ask what is that little vessel on the top of the stalk 
and what is the stalk itself? The vessel has been already spoken 
of as the capsule and the stalk is the seta, which lengthens with 
the development of the capsule or, strictly speaking, the 
sporogovium. The capsule and its contents are, collectively, the 
fruit. In our passage to a fuller description of this fruit, we must 
stop and see what provision is made for the reproductiou of mosses. 
We find no stamens and pistils, but we have male and female flowers 
by the co-operation of which repxoduction is effected through the 
spore generation as already explained. Among flowering plants, 
the stamens and pistils are commonly enclosed in the same floral 
envelope but, in many cases, they are in different flowers on the 
same plant, and in other cases, on different plants. You will prob- 
ably remember the terms hermaphrodite, monecious, and dicecious, 
Mosses are hermaphrodite, monoicous, dioicous, or polyoicous, that 
is to say, the antheridia and pistillidia may be(1) on the same plant, 
or (2) on different plants, or (3) on the same as well as on different 
plants. Inmonoicousmosses, the different organs may bein the same 
inflorescence or in separate inflorescences on the same plants. The 
Antheridium (anther-like) is a sac, shaped very much like a club. 
It consists of a single coat and encloses a great number of tiny cells, 
which are filled with a kind of mucilage. Each cell contains an 
antherozoid. The Antheridium opens at the top to discharge its 
contents. The antherozoid is a slender threadlike body, which, 
being furnished at its thin end with two cilia, is able to move freely 
about. ‘The Pistillidium is shaped very much like a Florence oil 
