274 



PLANT MORPHOLOGY 



cushion. Rhi/oids arise from the ventral surface; in Angiopteris and 

 Marattia they are unicelhilar, but in Danaea they are septate. The 

 anthoridia occur on both the upper and lower surfaces of the prothallium, 

 but the archegonia are confined to the lower side, where they are borne on 

 the thickened median portion. Both antheridia and archegonia are 

 sunken. They develop as in the Ophioglossales (Figs. 230 and 231). In 

 the archegonium a basal cell is usually formed in Marattia but not in 



B 



C D 



Fig. 230. Early stages in the development of the antheridium of Angiopteris evecta, X350. 



A. division of antheridial initial into primary wall cell and primary spermatogenous cell; 



B, anticlinal division of primary wall cell and periclinal division of primary spermatogenous 

 cell; C, further divisions of spermatogenous cells; D, slightly later stage, showing completion 

 of antheridial wall by cutting off of a layer of cells from adjacent cells of the prothallium. 

 (After Haupt.) 



Angiopteris and Danaea. There may be either two neck canal cells 

 or a single binucleate one. As in all ferns, the sperms are coiled and 

 multiciliate. 



Embryo. The development of the embryo is unlike either that of the 

 Ophioglossales or of the higher ferns. The first division of the fertilized 

 egg is transverse and a quadrant stage is organized. The two outer seg- 

 ments (those next to the neck of the archegonium) give rise to the foot, 

 the two inner ones to the stem and leaf, the leaf arising from the segment 

 nearer the apical region of the prothallium. The root appears later from 

 the inner portion of the embryo. A suspensor has been observed in some 

 species of Danaea and exceptionally in Angiopteris. 



Summary. Like the Ophioglossales, the Marattiales are homosporous 

 and eusporangiate, but the sporangia are borne on the abaxial side of the 

 leaves, usually in synangia. The sporangium wall consists of several 

 layers of cells and is without a definite annulus. The vernation is circi- 

 nate. The leaves have a pair of fleshy stipules. The gametophyte is 



