FERN CONFERENCE. 



501 



of the existence of a single initial cell in Phanerogams,* while 

 such a regular and definite type of meristematic construction is 

 absent in certain Thallophytes and Bryophytes, so that this can- 

 not be accepted as a decisive point. The presence of a single 

 initial seems frequently to follow a less robust habit : plants of 

 aquatic position are commonly of delicate texture ; most of the 

 lower forms are more or less distinctively aquatic : accordingly, 

 though many of the lower forms have a single initial cell, the 

 presence of a single initial need not necessarily be viewed as an 

 indication of low affinity, but rather it may, at least in some 

 cases, be the outcome of adaptation as regards bulk to a relatively 

 moist habitat. 



But it is in the characters of the gametophyte that the 

 affinities of the Hymcnopliyllacca to the Mosses appear to be 

 most obvious. The filamentous prothallus of the former is so 

 very like the protonema of the Moss, and the free protrusion of 

 the sexual organs beyond the general surface of the gameto- 

 phyte so striking in them both, and in some cases the repro- 

 duction of the gametophyte by gemmre so similar, that the 

 comparison hardly needs to be pointed out. But against these 

 similarities, which it is quite possible to imagine may have 

 arisen from adaptation of distinct stocks to similar external 

 conditions, is to be set the objection which will weigh most 

 heavily with many, and is specially alluded to by D. Campbell, 

 viz. that the leptosporangiate sporangium is quite unlike any- 

 thing found among the Bryophytes or Algns ; there is among 

 known forms none which gives a definite clue to such a transi- 

 tion as that which must have occurred if the Hymcnophyllaccce 

 were the original Ferns, and were derived from the Bryophytes. 

 It is true that Prantl has attempted to compare the sorus of the 

 Hymcnophyllaceai with the capsule of Anthoceros,f but a sug- 

 gestion which depends upon the conversion of the internal 

 sporogonous layer into a number of superficial sporangia, without 

 any evidence that such a conversion ever took place, here or in 

 any other series of plants, will hardly commend itself to the 

 reason as in any way probable. Moreover it is not apparent on 

 other grounds that there is any near affinity between Anthoceros 

 and the Hymcnopliyllaccce. 



* The most prominent example is the root of Hckocharis palustr's, 

 and it is to be noticed that this is a plant of aquatic habit. 



t Hymcnophyllacecp , p. 02. 



