THE OLDER Sl'OROl'HYTE 



205 



top of which is expanded so that it overarches the synangia. This ridge in section 

 appears T-shape. Whether this growth of leaf tissue between the synangia in 

 Dana-a is to be considered as an indusium may be questioned. It appears to be 

 very similar in structure to the oblong cavity or fovea, within which is sunk the not 

 very dissimilar synangium of Isoetes (fig. 189, B). 



THE SPORANGIUM OF THE MARATTIAC 1 I 



In Angiopterts and Archangiopteris there are formed separate sporangia not 

 very unlike those found in Botrychium or Helminthostachys, but in all the othei 

 genera the sporangia are fused into a synangium which might be compared with 

 the spike of Ophtoglossum. The synangium in Dun, in simplicifolia may reach a 

 length of over 3 centimeters and contain upward of 100 loculi. The first studv of 

 the development was made upon Marattia by Luerssen (Luerssen 3). According 

 to his statement, the differenti- 

 ation of the synangium begins 

 while the leaf is still very small 

 and rolled up between the stip- 

 ules. The tissue about a vein 

 begins to develop into an elevated 

 cushion following the vein. Upon 

 this receptacle there are devel- 

 oped two parallel ridges of tissue, 

 separated by a cleft. These two 

 ridges later grow upward and 

 meet above, so that their edges 

 completely close up the cleft, 

 which no longer shows from the 

 outside. In each half of this syn- 

 angium, very much as is the case 

 in the sporangial spike of Ophto- 

 glossum, there are developed sep- 

 arate archesporial groups corre- 

 sponding to the separate cham- 

 bers that are found in the fully 

 developed synangium. Luerssen 

 states that the whole process takes 

 about six months for its completion (fig. 186). 



In Angiopteris (fig. 187) the development of the sporangium begins at a much 

 later period, when the leaf is almost completely developed. The sporangia here are 

 arranged in an oblong group or sorus, which corresponds to the synangium in Marat- 

 tia. The formation of the sorus begins, according to Goebel, as an oblong depression 

 above a young vein, and about this depression there is formed a circle of short hairs 

 which are sometimes supposed to represent an indusium. Two ridges corresponding 

 to those found in the young synangium of" Marattia are formed, but upon these the 

 young sporangia develop separately, very much as they do in Botrychium. 



Goebel states that the archesporium in Angiopteris can be traced back to a 

 single hypodermal cell. This cell divides repeatedly but apparently without any 

 definite order, and there is finally formed a large mass of sporogenous tissue, each 

 cell of which gives rise in the usual way to four spores. The cells about the arche- 

 sporium develop the tapetum. Goebel states that these tapetal cells are destroyed 

 before the division of the spore mother cells, but I have found that this is not the 



Fig. iS$.—Maraiiia douglasii. 



A. Leaf from a young sporophyte. st, stipules. 



B. Leaflet with synangia. X4. 



C. Horizontal section of a synangium. Xio. 



X2. 



