140 



MANUAL OF BOTANY 



Fig. 898. 



only one appears above ground each year. Between this leaf 

 and the apex of the stem the rudiments of four other leaves 

 may generally be found, so that it 

 takes five years for a leaf to attain 

 its full development. 



The sporangia are borne upon a 

 peculiar outgrowth from the ventral 

 surface of the petiole of the sporo- 

 phyll, which has the appearance of 

 being branched, one branch bearing 

 an ordinary foliage lamina and the 

 other an elongated, sometimes 

 branched, spike-like structure, em- 

 bedded in or placed upon which 

 are the sporangia, arranged in two 

 rows, one on each side of its axis, or 

 variously clustered upon its surface 

 {fig. 898). 



The stem is very short and pre- 

 sents some peculiar features in its 

 interior. There is usually present 

 none of the sclerenchyma, so cha- 

 racteristic of the Ferns ; the ar- 

 rangement of the vascular structures 

 is different also, the Ophioglossacese 

 being schizostelic and the bundles of 

 the steles being collateral. Ophio- 

 glossum itself has no pericjde in 

 its steles. The genera Botrijcliium 

 and Helmintliostacliys possess 

 cambium in their collateral bundles, 



Fig. 898. OpMoglossum vulgatnm. a. Sporangia, h. Foliage leaf. 



but it does not give rise to much secondary tissue. Cork also 

 occurs in the cortex of these stems. 



