XIII 



EQUISETINEJE 



425 



lobed. In a number of cases a two-sided apical cell was seen 

 (Fig. 219), but its growth is very limited. Finally, a cell-mass 

 occasionally is the first product of germination. As a not 

 infrequent occurrence may be mentioned also the suppression of 

 the first rhizoid (Fig. 219, C). The development for some time 

 is so varied that it is impossible to give any rule for it, but 

 generally the prothallium at this stage, like that of the Icpto- 

 sporangiate Ferns, consists of but one layer of cells, and does 

 not show a midrib. These prothallia also do not have a 

 definite apical growth, and are usually more or less branched. 

 Often, however, the prothallium while still small has a some- 



FiG. 220. — A, Female prothallium with the first archegonium {ar), x 70 ; B, male prothallium, x 70. 



what cylindrical body composed of several layers of cells, and 

 in these the root-hairs are mainly confined to the base. The 

 chloroplasts which these at first contain are gradually changed 

 into leucoplasts, and may be completed absorbed.-" 



TJie Sexual Organs 



The prothallia of Equisetum are usually dioecious, and, as is 

 usual in such cases, the males are smaller and the antheridia 

 develop first. The latter generally appear in about a month. 

 In E. tebnateia there is not so much difference in the appear- 



1 Buchtien (i), p. 17. 



