MUSCINEAE. 



141 



the oldest parts behind die off. In this way the branches become ultimately 

 independent plants; this together with multiplication by gemmae, stolons, detached 

 buds, the change of rhizoids into protonema (in the Mosses) not only contributes 

 to multiply the number of individuals by asexual means to an extraordinary degree, 

 but is also the chief cause of the social growth of these plants ; many Mosses, even 

 such as only rarely bear ' fruit,' may in this way form close and extensive patches. 

 Sphagnum, for example, Hypnum, Mniiim, and others. 



The sexual organs are termed antheridia and archegonia. The antheridium when 

 mature is a spherical, ellipsoid or club-shaped body with a short or long stalk, the outer 

 cell-layer of which forms a sac-like wall, while the small cells enclosed by it, which 

 are vei}' numerous and crowded, each produce a spermaiozoid. The spermatozoids 

 are set at liberty by the rupture of the wall of the antheridium at its apex ; they are 

 spirally twisted threads with a thicker posterior and a sharply pointed anterior 

 extremity, and on the latter are two long delicate cilia, the vibrations of which cause 

 the movement of the spermatozoid. The female organs, which have been named 

 archegonia since Bischoff's time, are, when their oosphere is ready for fertilisation, 

 flask-shaped bodies which swell out into a pouch, the venter, above their narrow 

 base and end above in a long tieck. The tissue of the wall of the venter surrounds 

 the central cell, out of the lower and larger portion of which the oosphere is ultimately 

 formed \ A central row of cells is continued above this and runs all the way through 

 the neck up to the lid-cel/s ( ' stigmatic cells ' of authors) which lie on its apex. The cells 

 of this axile row, which are known as canal-cells, are disorganised before fertilisation 

 and changed into mucilage, which at length issues forth from the neck and forces 

 the four lid-cells asunder; thus an open passage is formed leading to the oosphere 

 and enabling the spermatozoids to reach it. 



The origin of the sexual organs of the IMuscineae varies in different species ; in 

 the thalloid forms of the Hepaticae they proceed from superficial cells of the thallus 

 or thallus-like decumbent stem behind the growing apex, or on special metamorphosed 

 branches as in many Marchantieae, but both antheridia and archegonia are formed in 

 the leafy Jungermannieae and in the Mosses from the apical cell of the shoot or from 

 its segments; in this case ihey may stand in the place of leaves or of lateral shoots or 

 even of hairs ; thus the antheridia in Radiila are formed in the axils of the leaves, in 

 Sphagnum in places where branches usually appear, in Fontinalis as apical growths 

 and at a later period in place of leaves ; in like manner the first archegonium on 

 fertile shoots of Andreaea and Radula is formed from the apical cell, the later ones 

 from its last segments ; the same is probably the case with Sphagnum. 



Antheridia and archegonia are usually produced in considerable numbers close 

 beside one another, and in the thalloid forms of the Hepaticae are generally 

 surrounded by later outgrowths of the thallus. In the leafy Jungermannieae and in 

 Mosses it is usual for several archegonia to have an envelope of leaves round them, 

 which is called 2, perichaetium ; in the Mosses the antheridia also are grouped together 

 in this way, and sometimes antheridia and archegonia are combined, but in the 

 Jungermannieae and Sphagnaceae the antheridia occur singly. Paraphyses, in the 

 form either of cell-filamenls or of narrow leaf-like cell-surfaces, frequently accompany 



Ihe archegonia are therefore oogonia of somewhat more comple.x construcli^>n. 



