392 Transactions. — Botany. 



the upper pinnules of the thallus, and on the upper side of the 

 pinnule : they are divided into numerous radially arranged 

 spores. Procarps small, terminal, on the upper pinnules of the 

 thallus, each with a single fertile cell. Cystocarps terminal, 

 protected by a single lateral branchlet. Fruit-mass built up 

 of 1 gonimoblast, divided into several rounded successively 

 formed gonimolobes. 



1. Pleonosporium brounianum, Harv.-Gibs. (= Cattithamnion 

 brounianum, Harv., Trans. Royal Irish Acad., xxii., p. 561). 

 Plate XXVII., fig. 2. 



Thallus dark-brown, 10-15 cm. high, irregularly alternately 

 (more rarely oppositely) pinnately branched in all directions, 

 with rhizoids descending along the whole length of the stem and 

 branches from the basal cells of the pinnae. The pinnules are 

 long and filamentous, and the lower ones clothe the stem and 

 branches with a matted mass of filaments, completely concealing 

 the general branch system. The main rachis has comparatively 

 few pinna?, but the pinnae are themselves pinnately decompound. 

 In typical specimens the last series of pinnules at the tips of the 

 branches are stout, more of less distichouslv corymbose and 

 arcuate. In many specimens the apices are completely covered 

 by filamentous pinnules growing up from below, which are pro- 

 longed beyond the growing-point in fastigiate masses. The 

 axils of the terminal pinnules are acute, and the cells of which 

 they are composed approximately square. As the frond is 

 descended the axils become more patent, and finally the pinnules 

 branch at an angle of from 60°-80°. The cells of the main stem 

 are about 300-400 /x long and 100-150 /x broad. The cells of 

 the pinnae are of a similar type but rather smaller, of the pinnules 

 very varied in relative dimensions. Those of the terminal pin- 

 nules are 40-50 /x long and 25-10/' broad; but in the filaments 

 cells may be obtained 150-200 /x long and only 25-40 /x broad. 

 The sporangia are placed on the inner sides of the pinnules, 

 rather sparsely at first. They are pear-shaped and undivided, 

 but afterwards contain 8, 16, or 32 radially arranged spores, 

 always more than 4 when mature. The cystocarps (according 

 to Harvey-Gibson) are binate, terminal, and invomcrate. An- 

 theridia unknown. 



Distribution. — Western Australia, Vict. ma {Bracebridge Wil- 

 son) ; Brighton, Dunedin {U. M. L) ; St. Clair (./. C. S.). 



This plant was first described from New Zealand by Pro- 

 fessor Harvev-Cibson from specimens collected by Professor 

 T. J. Parker (no locality given). As in the following species. 

 the vegetative structure is that of Spov</<>c/<>>ii>nit. but the spor- 

 angia fix it in the genus Pleonosporium. This plant may pos- 



