292 MOSSES AND FERNS chap. 



Short hairs occur upon the young sporophyte, and upon the 

 older plant there may be developed scales (palese) similar to 

 those found in the leptosporangiate Ferns. 



The base of the stipe, as well as that of the rachis of the leaf- 

 segments, is enlarged, closely resembling the "pulvinus" of a 

 leguminous leaf. The stalk breaks at this place, leaving a clean 

 scar. The smaller leaflets separate in the same way from the 

 rachis. 



The Marattiacese all develop conspicuous mucilage ducts 

 (Figs. 162, 163, m) and gum canals, very much like those 

 occurring in the Cycads (Brebner (2)). These ducts are of 

 two kinds. The first type is "schizogenic," i. e., of intercellular 

 origin, the secretory cells surrounding the intercellular canal. 

 The ducts of the second type are formed from the breaking 

 down of rows of tannin-bearing cells, which thus form irregular 

 ducts, not unlike certain milk-tubes of the higher plants. 



Upon the stipules and stipe there are often present lenticel- 

 like structures ("Staubgriibchen" of German authors). These 

 originate beneath stomata, in much the same way as the ordi- 

 nary lenticels ; but the cells below the opening of the lenticel are 

 not cork-cells, but small, thin-walled cells, which separate and 

 dry up, forming a dusty powder. 



Intercellular rod-like organs, composed mainly of calcium- 

 pectate, are of common occurrence. There may also occur 

 silicious deposits, and crystals of calcium-oxalate have been ob- 

 served in Angiopteris ( See Bitter ( i ) ) . 



The Sporangium 



The sporangia of the Marattiacese dififer most markedly 

 from the Ophioglossaceae in being borne on the lower side of the 

 ordinary leaves, and not on special segments. Except in 

 Angiopteris, they form synangia, whose development has been 

 especially studied in Marattia. Luerssen (7) describes the 

 process thus : "In Marattia the first differentiation of the spo- 

 rangium begins while the young leaf is still rolled up between the 

 stipules of the next older one. The tissue above the fertile vein 

 is more strongly developed than the adjoining parenchyma, and 

 forms an elevated cushion parallel with the vein. This is the 

 receptacle, which develops two parallel ridges, separated by a 

 cleft. These two ridges grow up until they meet, and their 

 edges grow together and completely close the cleft which lies 



