April, 1907.] Development of Sporangium of Eqidsetum. 125 



Later stages of the sporangium are similar to what Bower 

 found for E. limosum and E. arevense. A large number of 

 sporocvtes are developed, about forty in radial section, many of 

 which become disintegrated during the formation of tetrads. 



The most striking difference is in the first stage of the spor- 

 angium. The large cell (Fig. 1) which cuts off the first cell of 

 the sporangium is very sharply differentiated from its fellow's by 

 the size and structure of its nucleus and by the way its cytoplasm 

 stains. The lower cell and its descendants are distinctly dif- 

 ferentiated from the rest of the tissue through several stages of 

 the sporangium. The outer half of the large cell, the first cell of 

 the sporangium, always divides anticlinally which is contrary to 

 the usual method of division of the sporangial initial in the 

 Equisetales. Taking these facts into consideration together 

 with the position of this large cell, the conclusion is reached that 

 it is homologous with the sporangial initial figured by Bower for 

 E. arevense and that in E. hyemale the sporogenous tissue comes 

 entirelv from the primary wall cell while the inner cell is sterile. 



SUMM.A.RY AND COXCLUSIOX. 



1. Equisetum hyemale is the of eusporangiate type. 



2. The sporogenous tissue comes from a single cell. 



3. The first wall is periclinal the inner cell being sterile, 

 while the sporogenous tissue comes entirely from the outer cell. 



4. The tapetum comes from the cells surrounding the 

 sporogenous mass. 



5. There are two types of sporangia difl:ering in develop- 

 ment and governed bv the direction of the second division. 



6. Manv of the sporocytes are disintegrated during the 

 formation of tetrads. 



Bibliography. 



1. GoEBEL, K. "Beitrage zur vergleichenden Entwickef- 

 ungsgeschichte der Sporangien." Bot. Zeit. 38:545. 



2. Bower, F. O. "Studies in the morphology of spore 

 producing members. Equisetinese and Lvcopodineae," Rov. 

 Soc. Phil. Trans. 1S94, page 473. 



3. Campbell, D. H. "Structure and Development of 

 Mosses and Ferns," page 475. 



explaxatiox of plates. 



All figures were made with a Bausch and Lomb camera 

 lucida and a Bausch and Lomb 1-12 oil immersion 1.32 N. a. 

 objective with Leitz No. 4 ocular was used for all but Fig. 19 

 w^here a Leitz 1-7 objective with a No. 2 ocular was substituted. 

 The original magnification was approximately 1500 diametei^s 

 for all but Fig. \\) which was about 070 diameters. Drawings 

 were reduced to one-fourth diameter of original magnification. 



