Notes . 
73 
THE TRANSPIRATION OF THE SPOROPHORE OF 
THE MTTSCI. — In the account of the anatomy of the sporophore 
of Mosses which I have given elsewhere 1 , a thin-walled strand of 
tissue (which I have named leptoxylem) in the centre of the * central 
strand ’ is assumed, on anatomical grounds, to be that which conducts 
the transpiration-current up the seta to the apophysis, the organ of 
absorption and assimilation of gases and of transpiration. 
Recently I obtained material very suitable for testing by direct 
experiment whether indeed this leptoxylem does, or does not, conduct 
the transpiration-current. 
To do this I found that the best method was to make experiments 
with two different species of Moss ; in one of them the tissues were 
well differentiated, and in consequence rather large and opaque ; the 
other I chose on account of the transparency of its tissues, so that 
the transpiration-current could be observed without mutilating the 
tissues. The Mosses used were Polytrichum formosum , Hedw., and 
Splachnum sphaericum , Linn. The method adopted was that of 
placing the cut ends of the sporogonium in a drop of eosin. 
In the case of P. formosum, after a short time, about 30 minutes, 
on splitting up the seta and extracting the central strand and exa- 
mining it, it was found that the eosin had penetrated up the central 
part of the central strand only. But this did not show exactly into 
what tissues the eosin went ; therefore, a transverse section of 
another seta was made which had been treated similarly to the first, 
and this showed clearly that the eosin passed up the seta by means of 
the leptoxylem, although, as was only to be expected, the eosin, 
after some considerable time, penetrated into other tissues. The rate 
of transpiration could not be observed with any accuracy in P. formosum 
on account of the opaqueness of its tissues. 
In Splachnum sphaericum the rate of transpiration could, on account 
of the transparency of the seta, be observed with the greatest ease, 
the current going up the centre of the seta only; but on account of 
the extreme delicacy of the tissues the exact limits of the tissue which 
conducted the transpiration-current could not be determined. 
Watching measured distances of 2 mm. along a part of a seta, the 
eosin could be seen to move over the measured space in 2 minutes. 
1 Vaizey, On the Anatomy and Development of the Sporophore of the Musci 
(Part 1, Polytrichaceae). Journ. Linn. Soc. 
