MUSCI. 



?>15 



le formation of spores, even when, as in Archidium, it is subsequently supplanted 

 )y them ; a large part of the central tissue remains as the so-called Columella, and 

 [t is at the circumference of this that the mother-cells of the spores are formed, 

 'he structure of the mature capsule, and especially the contrivances for dispersing 

 le spores, are, however, so different in the various principal sections of Mosses 

 that it will be better to consider them more closely separately, and the more so 

 jcause by this means we shall at the same time arrive at the distinctive characters 

 )f the larger natural systematic groups. 



^In the mode of origin of the sporogonium there is, as might be expected, 

 ;ss variety. [The oospore is first of all clothed with a cell-wall, continues to grow 

 considerably, and is then divided by a horizontal or slightly oblique wall {basal 

 mil). The lower {hypobasal) of these two cells undergoes only one or two divisions, 

 id, as in Jungermanniese, contributes but litde to the formation of the embryo, 

 'he upper {epibasal) cell gives rise to the capsule and the seta : a two-sided apical 

 Jell is formed in it, by means of two oblique divisions.] Hofmeister asserts that in 

 'iryum argenteum the upper cell (that facing the neck of the archegonium) is divided 

 mce or twice by horizontal septa before the first oblique division, while in Phascum 

 id Andrecea this oblique septum is formed immediately after the first horizontal one. 

 'he apical cell now forms two rows of segments by partition-walls inclined alter- 

 lately, and these segments are next divided by radial vertical walls, followed by 

 irther numerous transverse divisions. By this process the young sporogonium is 

 ransformed into a multicellular body which is usually fusiform, the lower end not 

 'participating in the growth in length. A swelling of this lower end, such as usually 

 occurs in Hepaticse, takes place also in certain cases such as Sphagnum, Archidium, 

 and Phascum. The apex of the sporogonium now becomes inactive, and beneath it 

 the capsule is formed as a spherical, ovoid, cylindrical, or frequently unsymmetrical 

 swelling which originates, in the typical Mosses, only after the elongation of the 

 fusiform or cylindrical sporogonium, and after the raising up of the calyptra. The 

 internal differentiation of this mass of tissue, at first homogeneous, gives rise to 

 the various tissues which compose the capsule of Mosses, and especially to the 

 mother-cells of the spores which first of all become isolated and then divide so 

 as to form four spores. The contents of the mother-cell begin to divide into 



completely across it ; it forms simply a trabecula between the outer and the inner wall, which splits 

 into two lamella. Between these is the opening of the stoma. 



^ [The embryology of Mosses is treated of in the following works. Hofmeister, On the higher 

 Cryptogamia, Ray Soc. 1862. — Schimper, Rech. anat. et physiol. sur les Mousses, 1848. — Kiihn, 

 Entwick. d. Andreoeaceen, Bot. Mittheil. von Schenk und Luerssen, 1874 — Vouck, Entwick. d. Sporo- 

 goniums von Orthotrichum, Sitzber. d, Wien, Akad. 1876 — Leitgeb, Das Sporogon von Archidium, 

 ibid. 1879. — Kienitz-Gerloff, Bot. Zeitg. 1878. It appears that the tissue of the sporogonium presents, 

 at an early stage, a differentiation into an amphitheciutn, from which the wall of the capsule and of 

 the spore-sac are derived, and a central endothecium, corresponding to the future columella and 

 sporogenous layer. Leitgeb has however pointed out that in the Sphagnacege the sporogenous layer 

 is probably derived from the amphithecium. It is of interest to note also that, as Goebel has 

 pointed out, the spores of certain Vascular Cryptogams are developed, like those of Mosses, from a 

 layer of cells {archesporium), {vide irifra, p. 388). The development of the spores from a layer of cells 

 occurs also in the developing sporogonia of some Liverworts: it is distinct in Anthoceros, less so in 

 the Jungermanniese, still less in the Marchantiese, and does not take place in Riccia.'] 



