686 PROFESSOR P. O. BOWER ON 



the lateral branches sometimes forked, but usually simple ; in construction it corre- 

 sponds to that of Gleichenia (fig. 18, a), and the resemblance of the venation would 

 be very close if the lobation of the Gleichenia leaves were undeveloped and the leaf 

 entire. The next older leaf of the same plant showed equal dichotomy (b), each lobe 

 having scorpioid sympodial venation. In fig. 19, c, the leaf appears to be the coty- 

 ledon, but its branching is more advanced, the left-hand lobe having dichotomised 

 again. The process has gone further in fig. 18, d, but the inequality in the two 

 primary lobes is greater, though the number of lobes is the same in each. More- 

 over, the branching is clearly that of an anadromic helicoid sympodium. Com- 

 parison may, however, be made with the young leaf drawn by Tansley.* It 

 showed five lobes, one a " middle lobe," while each of the laterals branched again. 

 Assuming these branchings to be dichotomies, this frond " may be regarded as a sort 

 of prototype of the adult frond." Considering the facts that Tansley shows, and 

 the comparison that may be made with other Ferns, that assumption appears justified. 

 But if so, this is a case of a katadromic helicoid sympodium. We conclude that in 

 the young leaves of Matonia pectinata the branching is dichotomous ; but that it 

 may be sympodially developed, and fluctuates between the anadromic and kata- 

 dromic types. This is a particularly interesting conclusion in view of the archi- 

 tecture of the adult leaves in Matonia and Dipteris. The latter will be shown below 

 to be constructed on the anadromic scheme (Plate-fig. B) ; but the adult leaf of 

 M. pectinata is a katadromic sympodium (Plate-fig. A). The transition from the 

 state seen in Tansley's fig. 2 to the adult leaf of Matonia only presumes a continua- 

 tion of the katadromic sympodium thus initiated. The consequence of this method of 

 construction would be that the pinnae — that is, the weaker developed shanks of the 

 successive dichotomies — would appear constantly on the acroscopic side (katadromic 

 scorpioid sympodium) (Plate-fig. A). Comparing this with Helminthostachys, the 

 difference is that there the weaker shanks are thrown off on the basiscopic side 

 (anadromic scorpioid sympodium), while the branchings are fewer and less regular 

 than in Matonia. • 



The apparently divergent leaf of Matonia sarmentosa is built up of segments 

 with a venation and form like those of the juvenile leaves of M. pectinata. Its 

 branching was analysed by DiELS.t He concluded that it is essentially on the same 

 system as M. pectinata, but that the advance or suppression of the shanks of the 

 dichotomies occur alternately on the inner (acroscopic) and the outer (basiscopic) 

 limbs : " that is, they lead to a bostrychoid instead of a cicinnoid structure." The 

 matter has been reconsidered by Compton4 He finds the frond far less stereotyped 

 than in M. pectinata. " The rachis forks repeatedly, and one of two things may 

 happen : (l) both branches may develop more or less equally, forming elongated 

 axes, which fork again and again ; or (2) one of the branches may develop fully, 

 while the other, after bearing a very few (usually two) pinnae, ends in an aborted 



* L.c, fig. 2. f Natilrl. Pflanzenfam., i, 4, p. 343, fig. 180, B. \ New Phyt, viii, p. 299. 



