West. — A Contribution to the Study of the Marattiaceae. 407 
( 23 , p. 84) found that the tendency to dorsiventrality shown by older 
Angioptevis stems did not appear in Marattia , although the specimens of 
Marattia which she examined were gathered from steep banks ( 23 , 
P- 83). 
An examination of a very considerable number of plants of Angioptevis 
evecta of all ages and sizes was undertaken by the present writer in order 
to decide this question, with the result that of thirty-six specimens examined 
twenty were found to possess a strongly dorsiventral stem (cf. PI. XXII, 
Fig. 10), 1 six had an obliquely ascending axis, whereas only ten exhibited 
a strictly radial configuration of the stem. The present writer was therefore 
led to the opinion that the genus Angioptevis does show a marked tendency 
towards dorsiventrality, especially in older plants. Against the view that 
the change in direction of growth of the stem depends entirely upon the 
slope of the ground, it can be urged that several of the large plants of 
Datiaea nodosa examined by the author were gathered by Dr. Chandler 
from a very steep bank, and yet they exhibited a strictly radial symmetry. 
The statements of Miss Charles ( 23 , pp. 83-4) with reference to 
Mavattia alata also show that the configuration of the shoot is quite 
independent of the position of the plant. No signs of dorsiventrality were 
observed in Mavattia . 
In the case of the genera and species with upright radial axes, the 
skeletal framework is developed more or less uniformly all round, and, if 
we except the leaf-insertions, it is usually so, also, in the horizontal rhizomes 
of the adult sporophytes of Danaea alata and of Angioptevis evecta ; however, 
Shove ( 58 , p. 531) asserts that the specimen of Angioptevis which she 
examined presented definite dorsiventrality, not only in its external 
morphology, but also in its vascular anatomy, the meshes of the stelar 
lattice-work on the lower (= ventral) surface being long drawn out and with 
few anastomoses between the strands. 
The present writer agrees with Farmer and Hill ( 29 , p. 380) that the 
occurrence of large diamond-shaped gaps, similar in many respects to leaf 
gaps, upon the ventral surface of the skeletal framework of the markedly 
dorsiventral adult rhizomes of Danaea alata and of Kaulfussia indicates 
that the dorsiventrality, which these plants now exhibit, was probably ac- 
quired from a radially formed ancestor, the interior anatomical characters 
corresponding to such a disposition having been to a varying extent 
retained. 
In the following table the degree of dorsiventrality exhibited by 
young and old plants respectively of all the genera and species of Marattia- 
ceae at present known is summarized in convenient form : 
1 In the specimen of Angioptevis figured, which was quite an old plant, the bases of only two 
weakly developed leaves were found on the ventral surface of the stem ; the roots, on the other hand 
were restricted to the ventral surface. 
