254 Siphonocladiales 



Alga? (Urospora incrassata, Laminaria saccharina, etc.) or an endophyte in 

 the thallus of Enteromorpha spp. and N emotion spp., is usually placed in the 

 ValoniaceaB, although by some (Huber; Blackman & Tansley; Borgesen) it 

 is considered to belong to the Chsetophoracese. The coenocytes are epiphytic 

 on or embedded in the peripheral portion of the thallus of the host. They 

 are more or less globular, but with lobed and sinuate outlines. B. rldzopns 

 Reinke (the coenocytes of which are 54 90 yu, in diameter) is furnished 

 with one or more long colourless hairs, which project into the surrounding 

 medium, but B. arrhiza Wille has no such hairs. In B. rhizopus several 

 coenocytes are often arranged in a chain, being joined by intermediate 

 connecting tubes; the latter at first contain protoplasm and chloroplasts, but 

 the contents are later on withdrawn into the globular coenocytes which are 

 then cut off by septa. Sometimes new coenocytes arise by ' budding,' in 

 which case they are separated from the old ones only by a transverse wall. 

 The chloroplasts are numerous, rounded-polygonal in shape (as in the 

 Valonieae), and some of them contain a single pyrenoid. There are many 

 nuclei embedded in the peripheral protoplasm. Reproduction takes place 

 by quadriciliated zoogonidia (15 23 /* in length) which issue from a tube- 

 like extension of the coenocyte (Huber, '93). The exact position of the genus 

 Blastophysa is still to some extent doubtful, but the multinucleate character 

 and the fact that one species has a septate thallus are good reasons for 

 placing it in the Siphonocladiales and in proximity to the Valoniaceee. This 

 view is further strengthened by the nature of its chloroplasts and zoogonidia. 

 Its peculiar characters may be largely the result of its epiphytic or 

 endophytic habit. 



Sub-family SiPHONOCLADE^E. In all the genera of this group the primary 

 cylindrical coenocyte persists as a stalk or stipe, which is fastened to the sub- 

 stratum by unseptate or septate rhizoids. The basal part of the stipe (or, in 

 Cham&doris, the whole stipe) has annular constrictions, the only exception 

 being Struvea anastomosans, which is really a connecting link between 

 Struvea and Boodlea. In this basal part the cell-wall is thick and stratified. 

 Young erect ' shoots ' sometimes grow out from the rhizoids. The latter may 

 become creeping and rhizome-like, sending up new ' shoots ' in great numbers, 

 as in Chamsedoris. 



The septation of the thallus takes place by segregative cell-division, 

 except in Ernodesmis. This type of division ultimately results in oblique 

 walls in the upper parts of the thallus, each segment thus formed being able 

 to grow out into a branch ; and by a repetition of the process branches of the 

 second and third order are formed. The lentiform cells so characteristic of 

 Valonio are absent, although the verticillate branches of Ernodesmis originate 

 in a manner not very different from the growth of branches in Valonia. In 



