Howe : Phycological studies 247 



cell that was entirely destitute of them. The hyphae run, on the 

 whole, parallel to the direction of growth of the host, either singly 

 or laterally connate in bands of 2-4, occasionally with irregular 

 pseudo-parenchymatous anastomoses, as shown in figure i i. The 

 hyphae are 2.5-6/^ broad, and septate, the cells being mostly 4-15 

 times as long as broad and each containing one or more colorless 

 granules. No reproductive bodies have been observed. The fun- 

 gus* naturally suggests the epiphyte in Blodgettia confcrvoidcs Harv., 

 to which epiphyte Professor E. Perceval Wright* has restricted 

 the generic name Blodgetiia under the binomial Blodgcttia Bor- 

 netii, yet the two fungi are evidently different things, that on the 

 Siphonocladits not only lacking the "conidia" of the other, but 

 differing also in characters of the mycelium. Being uncertain to 

 what extent fungus and alga may be symbiotically related, we 

 have purposely omitted reference to the fungus in our specific 

 diagnosis, preferring to ground the species on the alga alone. It 

 is within the bounds of possibility that future investigations will 

 serve to emphasize the apparent analogies of Blodgcttia confervoides 

 and SipJionodadiis rigidus v^\\X\ the Lichenes and that some day 

 there may be recognized a group of marine lichens in which the 

 alga is the dominating symbiont. 



Petrosiphon %^\\. nov. 



A genus of Chlorophyceae of the family Valoniaceae.f Thallus 

 crustaceous, lightly coated with lime, firmly adnate to the sub- 

 stratum by ventral rhizoids and conforming to the inequalities of 

 its surface, composed of coherent irregularly septate tubes, these 

 dichotomously branched or laterally proliferous as in the genus 

 SipJionodadiis (without septum at base of branch) ; the determinate 

 progressive margin consisting of usually a single stratum of radi- 

 ally directed tubes, the older parts commonly showing in vertical 

 section several irregularly superposed tubes, mostly with a radial 

 direction, the central part, however, often consisting of vertical 

 tubes of limited growth and nearly equal length, springing from a 

 horizontal hypothallus. Cysts ( aplanospores ) frequent ; other 

 modes of reproduction unknown. 



The genus Petrosiphon is allied to SipJionodadiis Schmitz but 



* On Blodgcttia confervoides of Harvey, forming a new Genus and Species of 

 Fungi. Trans. Roy. Irish Acad. 28: 21-26. //. 2, 1881, 

 "I" See page 250. 



