DEVELOPMENT OF THE SPOROGONIUM IN THE MOSSES. 281 
iv. CONCLUSION. 
I may summarize as follows :— 
1. That the tissues of the central strand in the cases investi- 
gated consist of two kinds of tissue—the leptophloém, whose 
function is inferred on anatomical grounds (detailed in i. 2) to be 
similar to that of the phloém of Vascular Plants; and the 
leptoxylem, the function of which I originally inferred on ana- 
tomical grounds, but have lately (26), by direct experiment, 
determined to be that of conducting the transpiration current up 
the seta. 
2. That the apophysis of the Moss sporogonium is an organ for 
absorbing and assimilating gases, and that transpiration takes 
place from it must be fairly evident from the account of its 
anatomy given above, and it is in this respect similar to the 
leaves of the Vascular Plants. Its morphological value I cannot 
now discuss, but I hope shortly to be able to do so fully. 
. Although, as I have pointed out above, the stoma of the Poly- 
trichace® differs from what is typical in the Muscines, it is only 
à modification of that form, and does not differ in essential paints. 
The stomata of the sporophyte of the Muscinee generally belong 
to the same type as those of the Vasculares (see Pl. X.). 
Leitgeb (15) has shown that the so-called stomata of the 
oophyte of the Marchantiacex are essentially different from the 
true stomata of the sporophyte of the Muscine® and Vascular 
plants. 
3. The foot is the organ of absorption of liquids, although it 
does not present the ordinary form of a root, as it does not show, 
80 far as I bave been able to determine, any sign of endogenous 
growth. The root of Phylloglossum, which, according to Bower 
(3), is not endogenous in origin, may perhaps form a connecting- 
link between the foot of the Muscineæ and the root of the 
Vasculares. From the fact of the parasitic habit of the sporo- 
phyte of the Muscineæ, the absence of a root-cap is hardly sur- 
prising, as that organ is lost in many parasitic plants altogether ; 
and in those in which it is present in the embryonic primary 
root, e. g. Viscum, it is lost, according to Solms-Laubach (24), 
When the young plant begins to grow parasitically into the 
tissues of the host. 
LINN. JOURN.—BOTANY, VOL. XXIV. 
