224 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
The author is of opinion that neither the anatomy nor the morphology 
of the Hymenophyllaceee lends itself to the view that they present an 
archaic form from which all other ferns are derived. 
Stem of Ophioglossacese.* — In contrast to the statement of other 
writers, and to his own previous view, M. P. Van Tieghem now regards 
the stem of all the genera of Ophioglossacem as monostelic in the tigellar 
portion, i. e. below the first leaf, and astelic (i. e. without any central 
cylinder) in the portion of the stem above the first leaf. The difference 
which is manifested between the two types of stem in the order — viz. that 
of Ophioglossum on the one hand and that of Botrychium and Helmintho- 
stachys on the other hand — consists really in this, that in the former case 
the vascular bundles are free or dialydesmic, in the latter case they 
coalesce laterally, or are gamodesmic. This astelic structure of the stem 
marks a divergence from the Eilicineas, and brings the Ophioglossaceae 
nearer to the Equisetacese, where we have also the astelic structure, both 
dialydesmic and gamodesmic. 
Algae. 
Symbiosis of Algae and Animals-t — Mdme. A. Weber-Van Bosse 
and Prof. M. Weber describe the following new example of true or 
apparent symbiosis from the Dutch East Indies. 
A filamentous alga, Trentepohlia spongophila n. sp., was found in a 
freshwater lake in Sumatra, imparting a green colour to the sponge 
Ephydatia fluviatilis , and producing zoospores. The alga alone appears 
to derive benefit from the commensalism, but the sponge does not suffer 
injury from the perforation of its tissue. This is, therefore, not an 
example of true parasitism, but is rather a transitional case between true 
symbiosis and parasitism. 
True symbiosis was observed between a marine sponge belonging to 
the genus Halicliondria and Struvea delicatula ; the former growing to a 
larger size than usual when infested by the alga, which becomes some- 
what modified and assumes the appearance of Spongocladia vaucherioe- 
formis. 
MarcJiesettia spongioides was found in symbiosis with a Beniera. 
The authors enumerate the following as true examples of symbiosis : — 
Struvea delicatula with a Halichondria ; Marchesettia spongioides with 
Beniera fibulata ; Spongocladia vaucheriseformis with Beniera Jibulata ; 
Oscillaria spongelise with Spongelia pallescens and Psammoclema ramosum. 
The following are doubtful : — Callitliamnion membranaceum with Spongelia 
pallescens , S. spinifera , and Aplysilla sulfur ea ; Scytonema with Spongia 
otaheitica. The following must be regarded as instances of parasitism : — 
Thamnoclonium Jlabelliforme on Beniera fibulata ; the Floridea observed 
by Lendenfeld on Dactylochalina australis ; Thamnoclonium spongioides 
and Bhodymenia palmetta on an undetermined sponge; Trentepohlia 
spongophila on Ephydatia fluviatilis. 
* Journ. de Bot. (Morot), iv. (1890) pp. 405-10. 
f ‘Zool. Ergebnisse einer Keise nach Niederlandisch Ost-Indien,’ Heft i. 
pp. 48-71 (1 pi.) Leiden, 1890. See Bot. Centralbl., xliii. (1890) p. 118; and Ann. 
Jard. Bot. Buitenzorg, viii. (1890) pp. 79-94 (2 pis.). 
