138 W. M. Bale: 



A singular condition noted by Billard as occurring in A. vitiana 

 and Idia prisfis is observable also in A. brevirostris, namely, the 

 reversal of the front and back of the polypidom. I have once 

 observed the same thing in A. sinuosa, but it would seem to be a 

 common occurrence in .4. hrevirosfris, as it is found in more than 

 one of my few specimens. In one instance a branch has the hydro- 

 cladia up to about the middle all fronting one way. suddenly a 

 reversal occurs, and the hydrocladia face in the opposite direction; 

 this continues for a distance including four hydrocladia on each 

 side, and then a second reversal takes place, and on the rest of the 

 branch the hydrocladia face as at the beginning. In another case 

 the part of the shoot including the first five hydrocladia faces one 

 way, and the remainder in the opposite direction. Billard found 

 that these reversals followed a regeneration of a broken part; in my 

 specimens, however, this did not appear to be the cause, as I could 

 find not the slightest breach of continuity in the branches. 



The corbulae of A. hrevirosfris are interesting structui'es, com- 

 bining, as I pointed out in 1881, the general character of the 

 A. pluma type with the presence of hydrothecae on the leaflets. 

 The attachment of the leaflets to each other by the marginal lobes, 

 leaving small interstices between, is a feature found also in the 

 corbulae of A. macrocarpa. Another noteworthy feature is the 

 continuation of the gonocladium beyond the corbula, where it 

 resumes for a short distance the character of a hydrocladium, sup- 

 porting one or two hydrothecae. 



Lytocarpus aukitus (Busk). (Plate XIII., Fig. 10). 



Plumul(tri(i (iiiritti. Busk, Voy. of Battlesn., i., 1852, p. 



397. 

 AfflaopJunld (nirita. Bale, Aust. Hydi'. Zoopli., 1884. p. 



169. pi. xviii.. figs. 18. 19. 

 Liltocdv pitx phd n'i<'('\is (iiirlttis, Billard. ('. K. Acail. d. 

 Sei.. cxiviii.. 1909. p. aOT ; id.. Ann. d. Sci. Nat.. 9 ser., 

 xi.. 1910. p. 4i). 

 AiilaophfiiKi (lls'iiiiictd . Pictrt. Rev. Suisse dc Zoo!., i., 

 189:5. }.. r)9. pi. iii.. figs. .')1. 52. 

 HydrophytoTi 2-."! imlii's in heiglit. polysiphonic in the older 

 portions oidy. and sTiiall spcH'iniciis monosiphonic throughout, 

 branched or unl)iaiKhcd ; bi-anchi's wIkmi present all in one plane, 

 given off almost at right angk's fioni the sujiplementary tul)es. each 

 internode normally supporting a hydrocladium, but the uodt's often 

 indistinct. Hydrocladia straight, alternate, divergent at a wide 



