EQUISETACE^. 



363 



prothallia are, in E. Telmakia, usually narrow and ligulate, and consist of but a 

 single layer of cells. The older prothallia are, both in this and in other species, 

 branched in an irregularly lobed manner ; one of the lobes takes, sooner or later, 

 the lead in growth, becomes thicker and fleshy, consisting of several layers of cells, 

 and puts forth root-hairs from its under side. 



The prothallia of the Equisetaceae are, in general, dioecious. The male pro- 

 thallia remain smaller, attaining a length of a few millimetres, and produce archegonia 

 only in exceptional cases on shoots of later 

 origin (Hofmeister). The female prothallia are 

 larger (as much as i inch) ; Hofmeister com- 

 pares them to the thallus oi Anthoceros purictatus^ 

 Duval-Jouve to a curled endive-leaf. Duval- 

 Jouve states that the antheridia appear about 

 five weeks after germination, the archegonia 

 much later. These statements refer especially to 

 E. arvejise, limosum, and palustre ; according to 

 the same writer, the prothallia of E. Telmateia 

 and sylvaticum are broader and less branched ; 

 those o{ E.ramosissinmm and variegatinii slenderer 

 and more elongated. 



The Antheridia arise at the end or margin 

 of the larger lobes of the male prothallium. 

 The apical cells of the enveloping layer of the 

 anlheridium contain but little or no chloro- 

 phyll ; they separate from one another on the 

 addition of water (like those of Hepaticae), to 

 allow the escape of the antherozoids, which are- 

 still enclosed in vesicles and number from 100 

 to 150. The hindermost and thickest of the 

 two or three coils of the antherozoid, which is 

 larger in this class than in all other Crypto- 

 gams, bears an appendage on the inner side 

 which Hofmeister terms an undulating Float, 

 Schacht a thin-walled vesicle of protoplasm, and 

 which contain granules of starch and sap (com- 

 pare with Ferns and Lycopodiaceoe). 



The Ai'chegonia are developed from single 

 cells of the anterior margin of the thick and 



fleshy lobes of the female prothallium. As the tissue of the prothallium be- 

 neath them continues its growth, the archegonia come, as in Pellia, to stand 

 on its upper surface. The mother-cell of the archegonia, after it has become 

 much curved, divides by a wall parallel to the surface of the prothallium ; the 

 lower of the two daughter-cells, which is entirely sunk in the tissue of the pro- 

 thallium, becomes the central cell; from the outer one is formed the neck, con- 

 sisting, at a subsequent period, of four parallel rows of cells. The four upper 

 cells become very long ; the four middle ones remain shorter ; the four lower 



Pig. 269.— First stage of development of tlie 

 prothallium of Eguiseium Telmateia ; tu the first 

 root-hair; / rudiment of the prothallium. The 

 order of development follows the numbers I—l'I 

 {X about 200). 



