HEP A TICyE 



157 



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of vascular bundles in the form of cambium-strings, and is furnished 

 with a slightly differentiated epidermal layer. In the thalloid forms the 

 thallus is composed of a more or less thick plate of tissue, which in 

 one order, the Marchantiacese, possesses on the upper side a strongly 

 developed epiderm, provided with stomates of very peculiar form, unlike 

 anything that occurs elsewhere in the vegetable kingdom. 



The first result of the germination of the 

 spore is either a filiform protoneme, a flat plate 

 of cells, or a mass of tissue ; but the differentia- 

 tion of the protoneme from the sexual genera- 

 tion is not so well marked as in the IMusci. The 

 non-sexual propagation of the Hepaticce takes 

 place either by innovation^ i.e. by the continual 

 dying away of the stem behind, or by j^enwKB, 

 which exhibit a high degree of development. In 

 the thalloid genera Marchantia (L.), Lunularia 

 (Mich.), and Blasia, these gemmae are found in 

 peculiar outgrowths of the upper surface of the 

 thallus known as cupules, which are cup-shaped 

 in Marchantia (see fig. 150), crescent-shaped in 

 Lunularia, flask-shaped in Blasia. From the 

 base of these cupules there spring hair-like 

 papillae, the apical cells of which divide re- 

 peatedly in both directions, and constitute the 

 gemmae. In some of the foliose genera, e.g. 

 Madotheca (Dum.), the gemmae are formed out 

 of cells belonging to the margin of the leaf, 

 and simply detach themselves. Vochting states 

 that in Lunularia, and Marchantia also, isolated 

 masses of cells possess the power of regenera- 

 tion or development into new individuals, to 

 whatever part of the thallus they may have be- 

 longed. Shoots resembling a normal thallus 

 spring from the pedicel of the inflorescence of 

 Marchantia polymorpha (L.) when lying pros- 

 trate on the soil. 



The locality of the sexual organs of reproduction, antherids and 

 archegones, varies in the different orders. In one genus, Anthoceros 

 (Mich.), they are endogenous, or originate in the tissue of the thallus 

 itself ; in the remaining thalloid forms they are produced on the upper 

 side of the thallus ; and in the ]\Iarchantiaceae on special vertical out- 

 growths, some of which bear antherids on their upper, others archegones 



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Fig. 132. — yungcrmantiia 

 nemorosa L. (x lo). 



