ON GENERA AND SPECIES. 15 



primary veins, they thus become parallel with the costse, 

 and are then called transverse. In many cases the venules 

 produce veinlets in an irregular manner, which either anas- 

 tomose, or terminate within the areoles. When directed 

 outwards they are termed excurrent, and recurrent when 

 directed inwards ; this is termed compound anastomose 

 venation. In many cases, both in free and anastomose 

 venation, the apices of the venules and veinlets is thickened 

 (clavate) in the form of a gland. 



RECEPTACLES. 



The receptacles are the sites upon which the sporangia 

 are seated, and are generally thickened points, or length- 

 ened portion of some part of the venation. In position 

 they are called terminal when on the apex of the veins or 

 their branches ; lateral when on the sides of the veins ; 

 axillary when on the forking ; compital when on the 

 angular crossing or points of confluence of two or more 

 venules or veinlets. They are superficial or immersed in 

 the substance of the frond, or elevated above its surface, and 

 then columnar or globose. When in the form of a point 

 or dot they are termed punctiform, and, when lengthened, 

 elongated or linear ; and amorphous when of no denned 

 form (as in Acrostichum). 



SPORANGIA. 



The spore cases or sporangia are the organs which con- 

 tain the reproductive spores, and are borne in masses upon 

 the receptacles. They are thin and transparent, or horny 



