EQUISETINEAE. 



tl 





the cell which contains chlorophyll is slightly inclined to the longitudinal axis of the 

 young plant (being sometimes dichotomous in E. Telmateja), and the two cells thus 

 formed develope into separate tubes ; in other cases this cell developes into a longer 

 tube, the apical portion of which is cut off by a transverse wall, as happens sometimes 

 in E. arvense. 



Cell-surfaces are formed as growth continues; branches arise as outgrowths 

 from lateral cells and develope in a similar manner ; and as the cells multiply, the 

 chlorophyll-corpuscles which they contain are also constantly being multiplied by 

 division. The young prothallia are usually ribbon- 

 like and narrow, and formed of one layer of cells 

 in E. Telmateja ; the older prothallia in other species 

 and in E. Telmateja also are irregularly lobed ; one 

 of the lobes sooner or later outstrips the others and 

 becomes thicker and fleshy, being formed of several 

 layers of cells, and puts out rhizoids on its under 

 side. 



The prothallia of the Equisetaceae are for the 

 most part dioecious; the male are always smaller, 

 a few millimetres long, and according to Hofmeister 

 produce archegonia only exceptionally and on late 

 shoots. The female are much larger, reaching 

 a half inch in length ; Hofmeister compares them 

 to the thallus of Anihoceros punctatus, Duval-Jouve 

 to a curly endive-leaf. Sadebeck avers that antheridia 

 may appear at a later period on the lobes of female 

 prothallia. It is probable that in this as in other 

 cases the male prothallia are those which have been 

 insufficiently fed; at least the observation of Hof- 

 meister just mentioned, that they can afterwards 

 produce archegonia as well as antheridia, points to 

 this conclusion (see p. 198). These statements refer 

 chiefly to E. arvense, E. limosum, and E. palustre ; 

 according to Duval-Jouve the prothallia of E. Telma- 

 teja and E. sylvaticum are broader and less branched, 

 those of E. ramosissimum and E. variegatum are 

 more slender and elongated. 



The antheridia appear at the extremity or 

 on the margin of the larger lobe of the male 

 prothallium. The apical cells of the layer which envelopes the antheridium con- 

 tains little or no chlorophyll, and like the same cells in the Hepaticae they separate 

 from one another when they come in contact with water, and release the spermatozoids 

 which are still inclosed in cysts and may be from one hundred to one hundred and 

 fifty in number. The spermatozoid is larger than in other Cryptogams and forms 

 two or three coils, and the posterior and thicker coil carries an appendage with it on 

 its inner side, a vesicle such as is seen in the spermatozoids of the Ferns, containing 

 granules of starch and cell-sap (compare Filices and Isaeteae). The mother-cells of 



M 



FIG. 209. First stages in the develop- 

 ment of the prothallium of Eqiiisetum Tel- 

 mateja ; iu the first rhizoid, t rudiment of 

 the thallus ; the numbers from /to K/indicate 

 successive stages of development. Magn. 

 about 200 times. 



