THE HIGHER CRTPTOGAMIA. 293 



of the protliallium have reached the stage at which the 

 protoplasm of their contents clothes the inner wall in the 

 form of a thin layer, they have a manifestly vesicular ap- 

 pearance. I have often clearly observed their multiplication 

 by division (PL XXXVII, fig. 20). Mucilaginous threads 

 radiate from the nucleus. 



However various the ramifications of the prothallium 

 may be at first, the final result is always the same. One 

 or more (five at the most) of the numerous shoots develope 

 themselves much more vigorously than the others in length, 

 breadth, and thickness. Their outline resembles to some 

 extent that of the prothallia of the ferns. The subse- 

 quently formed capillary roots of the prothallium are pro- 

 duced almost exclusively from their under side. Sexual 

 organs are mainly produced from these principal lobes; 

 they seldom occur on other parts of the prothallium. 



The prothallia of Equisetum arvense, pratense, and 

 palu-stre, are distinctly disecious. The individuals which 

 bear antheridia produce them very plentifully, but yield 

 archegonia only in the rarest instances, and then upon late 

 shoots of the base of the prothallium. These may be con- 

 sidered as new individuals, by analogy to the processes 

 which spring from the marginal cells of old fern-prothal- 

 lia. The male prothallia do not attain the full size 

 of the females. They consist normally of only one or two 

 thickly fleshy expansions of cellular tissue, whose margins 

 bear the antheridia, and also some thin membraneous 

 barren shoots. Their chlorophyll contrasts with that of 

 the female prothallia by a manifest tendency to a yellow 

 colour. The deep-brown colour Avhich is assumed by 

 empty antheridia, imparts a diseased appearance to the 

 male prothallia at an early period. 



The production of an antheridium is preceded by fre- 

 quently repeated division of one of the marginal cells by 

 means of septa inclined alternately in two directions (PI. 

 XXXVIII, fig. 24). The cells of the second degree divide 

 by radial longitudinal septa, and each of the three-sided 

 cells thus formed divide into inner and outer cells by septa 

 parallel to the axis of the organ. The latter become the 

 covering layer of the antheridium, and numerous chloro- 



