EQUISETACE^ 



103 



rapidly disappears entirely ; it undergoes no further division, but elongates 

 rapidly into a long hyaline rhizoid. The larger of the two primary cells, 

 which still contains abundance of chlorophyll, divides further by walls, at 

 first in two directions only, into a multicellular plate which increases 

 rapidly by apical growth, and soon branches in one plane. A difference 

 is now set up between the develop- 

 ment of the male and female pro- 

 thallia. The former remain com.- 

 paratively small and narrow, and 

 the cell-division continues in the 



Fig. 78. — A, male prothallium of Eqtdsetrijn 

 arvense L. ; a, antherids ( x 200). (After Hof- 

 meister.) B — jET, antherozoids of ^. niaxii)iiim 

 Lam. in different stages of development 

 (X1200). (After Schacht.) 



two directions only : they consist, 

 therefore, permanently of only a 

 single layer of cells, and display 

 but little lobing. Their colour is 

 yellowish green. The female pro- 

 thallia, on the other hand, grow to 



a considerably larger size, as nmch as half an inch in length, are of a 

 deeper green colour, and at an early period form a number of lobes at 

 their anterior portion, which consist of masses of merismatic tissue, cell- 

 division taking place in the tangential as well as the other two directions ; 

 they branch also in the same plane much more abundantly than the male 

 prothallia. The formation of female or male prothallia appears to depend 



Fig. 79. — Vertical section of lobe of female pro- 

 thallium of E. art'ense. a, archegones ; //, 

 rhizoids ( x 600). (After Goebel.) 



