DEVELOPMENT OF THE SPOROGONIUM IN THE MOSSES. 263 
dealt with anything more than the external characters. He, I 
believe, was the first to show that the sporogonium was not an 
integral portion of the moss-plant, but grew as a separate or- 
ganism attached to the oophyte in a way somewhat similar to 
that by which a parasite is attached to its host; he described 
also the intercellular space surrounding the spore-sac. 
It remained, however, for an Englishman, William Valentine 
(27), to publish in 1833 the first account of the early develop- 
ment of the sporogonium. He also seems to have noticed that 
the tissues of the seta were differentiated into a cortical layer 
surrounding an axial cylinder, but he did not further investigate 
their respective characteristics. He describes the termination 
of the foot in two forms which he regards as exceptional, but 
which show a certain amount of similarity to what I have found 
among the Polytriehaces generally. Valentine describes the 
structure of the sporangium accurately. 
In the same year that Valentine's work appeared in England, 
Hugo von Mohl (18) published an account of the anatomy and 
development of the spores of the Musci, and an account of the’ 
structure of the theca. 
Lantzius Beninga (13) published in 1847 the result of his 
valuable work, which dealt exclusively with the theca, especial 
attention being paid to the peristome. He gave a description of 
the intercellular spaces and trabecular tissue found internally 
to the pore-sac in the higher Polytricha. 
Hofmeister (9) in 1851 published a work on the higher Crypto- 
gams, in which the Musci are dealt with. The earlier stages of 
development of the sporogonium are described, but the later only 
in the case of the theca and spores. 
Lorentz (17) published in 1867 a fuller account of the ana- 
tomy of the Mosses than had ever before appeared; but his 
knowledge was only obtained from transverse sections of the 
organs and tissues with which he dealt. Some of his work is. 
discussed below in detail. The chief result of Lorentz's work, 
so far as the sporogonium was concerned, was to show that there 
Was a specialized axial cylinder of tissue which he called the 
“central strand." He also described the two forms of tissue of 
which the central strand consists, namely, a thick-walled hollow 
Cylinder of tissue surrounding a solid axial cylinder of thin- 
walled cells. 
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