394 Transactions. — Botany. 



older and infertile specimens. It is very different in appearance 

 from them, for the rhizoids are undeveloped. After the sporangia 

 are discharged the colourless cases remain behind, and appar- 

 ently only gradually decay. 



Genus 6. Callithamnion (Lyngbye). 



Thallus upright, much dichotomised or laterally branched 

 on all sides (or distichous in the upper part), with monopodial or 

 svmpodial arrangement. The branches consist of single rows of 

 naked cells with more than one nucleus. The main branch 

 frequently coated with rhizoids below. Sporangia in tetrads 

 (sometimes cruciate according to some) on the upper branches of 

 the thallus, attached laterally on the upper side (one or more on 

 a single cell). Antheridia generally very small, consisting of 

 thickly packed bundles of very various but analogous arrange- 

 ment to that of the sporangia. The cystocarps attached laterally 

 to the upper part of the thallus (more rarely apparently ter- 

 minal), without an involucre, consisting of a pair of gonimoblasts 

 (more seldom one), which put forth on a smaller central cell 

 several successively formed rounded gonimolobes. 



1. Callithamnion byssoides, Arnott (Harv.. Fl. N.Z.. ii.. 260 ; 

 J. Ag., Epicr. Florid., p. 29). 



Thallus somewhat erect, alternately pinnately decompound, 

 corticated at the base only, very flaccid, with the branches and 

 branchlets coming out from all sides, the upper branchlets 

 dichotomous and incurved, sublanceolate in outline, equal in 

 length or shorter than the one on the inside. Tetraspores sparse 

 on the inner side of the axils, the young ones obovate-elavate. 

 ripe ones subrotund in tetrads. I have seen no description of 

 cystocarps or antheridia, but the former at least are known. 



Distribution. — The warmer Atlantic shores of Europe and 

 America ; Tasmania. 



Var. caulescens (J. Ag., Epicr. Florid., p. 39), with a firmer 

 stem which is corticated for a considerable distance upwards 

 with decurrenl threads enclosed in a membrane. Foveaux Strait 

 and Otago Harbour (Lyatt) ; Maketu (Chapman) ; < >tago Har- 

 bour (./. C. 8.). 



The specimens I have seen, collected at the Maori kaik (Dun- 

 edin Harbour) by Mr. J. C. Smith, belong to Agardh's var. 

 caulescens, which is probably a distinct species. The main axis 

 and all the branches are corticated, the plumules alone being 

 free. The articulations of the main stem and branches are thus 

 completely hidden. The plant is 15-20 cm. high, irregularly 

 alternately branched. The terminal pinnules are dichotomous. 

 incurved, and subcorymbose at the tips. The lower portions of 



