246 



THIRD GROUP.— VASCULAR CRYPTOGAMS. 



into an axile bundle of more elongated and a rind of shorter parenchymatous cells, 

 and the upper surface is clothed with rhizoids ; it is from two lines to two inches 

 long and from a half to one and a half line broad. The prothallium of Botrychium 

 Lunan'a is, according to Hofmeister, an ovoid firm mass of cellular tissue, the greatest 

 diameter of which is not more than a half line and often much less (Fig. 201), light 

 brown on the outside and yellowish white within, and furnished on every side with 

 scattered rhizoids of no great length. These prothallia are monoecious, and each 

 produces a number of antheridia and archegonia pretty equally distributed over its 

 entire surface ; there are none on the primary tuber in O. pedimculosiim ; in Botrychium 

 the upper side which is towards the surface of the ground chiefly bears aniheridia. 

 The aniheridia are cavities in the tissue of the prothallium, covered on the outside 

 with a few layers of cells and only slightly projecting in Ophioglossum. In this genus 

 the mother-cells of the spermatozoids are formed by repeated divisions from one or 

 two cells of the inner tissue, which lie beneath one or two external layers ^ The 

 mother-cells form a roundish mass of tissue which slightly raises the covering layers, 

 and, as in Botrychium, produce the spermatozoids, which are of similar form to those 



of the Polypodiaceae, but 

 larger, and escape through 

 a narrow orifice in the roof 

 of the antheridium. The 

 archegonia appear to follow 

 the course of development 

 observed in the other Vas- 

 cular Cryptogams, and the 

 statements . of Mettenius 

 agree entirely with what is 

 known respecting the for- 

 mation of the archegonia 

 in the rest of the Filicineae. 

 The venter of the archego- 

 nium is wholly sunk in the prothallium, and only the neck, which is usually very 

 short, projects above the surface. 



The asexual generatioft [sporophore, sporophyte). The manner in which the 

 oospore developes into the embryo is not known, but it probably agrees with that of 

 the other Filicineae; we gather from the statements of Hofmeister and Mettenius 

 that the orientation only of the organs in it is different. 



The mode of growth in the developed plant is in some respects remarkable. 

 The stem, which in Ophioglossum and Botrychium is buried deep in the ground, 

 appears never to branch in Ophioglossum, while several cases of branching have been 

 described by Roeper and Holle in Botrychium. Even the comparatively thick roots 

 of Ophioglossum do not branch, but many of them give rise to adventitious buds which 

 develope into new plants ^ The roots oi Botrychium on the contrary do not produce 

 adventitious buds, and they not unfrequently form a number of lateral branches. 



As in Mai-attia {vid. infra). 



The Ophioglosseae become perennial as well as multiply by means of these adventitious shoots. 



