FRE.SII \\ AT i:R ALG^E OF THE UNITED STATES. 181 



remarkable from the fact that, whilst in many cases the little branches which pro- 

 duce tlif anthcridia gi\- origin to the spores also, in others they do not; so that 

 there are numerous antheridia, which are unconnected with any female organs. 

 When a branch does produce both of the reproductive organs it usually forks into 

 three short hranclilets, thus giving origin to a pair of sporangia and a single curved, 

 hooked antheridia. Sometimes, however, there is but a single female branchlet, 

 and I have even seen a sporangium, immediately sessile upon a branch, which at 

 its ape\ .rave origin to a male organ. In the coat of the perfected spore, I have 

 not been able to find more than two distinct strata. 



Figs. 3 and 3 a, pi. 20, represent sporangia and antheridia of this species ; 3 i, 

 a simple, young and only partly formed antheridia, magnified 160 diameters; 3 c, 

 a perfected spore magnified 260 diameters. 



V. sericea, I.YNUBYE. 



V. aquatica vel terreatris, cseapitosa, vel aordide vel laete vel lateolo-viridis ; thallis tcnuibns, 

 dense intricatis, laxe et vage ramosis, ramisquc saepe adseemlentibus vol erectia ; oogoniis ses- 

 silibus vel brevissime pedicellatis, 1-6 scriatis, nnilatoralibus, oblique et enormiter ovalibua, 

 ore lateral! producto rostellutis ; antheridiis in thallo ips<> jnxta oogoniia sessilibus* cylin- 

 drareo-subclavatis, deflcxis; apcrmatozoideis oblongis, puncto rubro notatis (teste de Bury), 

 in utroque polo cilio uuico pneditia. 



Syn. V. ai-ersa, HASSALL, Freah- Water Algaa, p. 54. 



V. sericea, LYNQBYE. KAHKMIUHST, Flora Europ. Algarum, Sect. III. p. 271. 



Hub. I* rope Philadelphia; Wood. 



Aquatic or tcrreatrial, occurring in turfy mats of a yellowish, dirty, or bright green color; fronds 

 thin, densely intricate, laxly and vaguely branched, often together with the branches ascending 

 or erect; oogonia sessile or very shortly pedicellate, 1-6 seriate, unilateral, obliquely irregu- 

 larly oval, their lateral mouths produced into a rostellum or beak ; antheridia sessile upon the 

 thallus itself near the oogoniura, somewhat cylindrical, subclavatc, deflexed especially in age ; 

 spermatozoids (according to De Bary) oblong, marked with a red point and furnished with a 

 single cilia at each end. 



rks. I can perceive no constant differences between V. sericea, Lyng. and 

 V. azrsa, Hass. The extreme forms differ somewhat, but both are very common 

 about Philadelphia, and everywhere grade into one another. Prof. Rabenhorst 

 thinks that the two forms are scarcely distinct, and states that the most character- 

 istic differences are, that in V. aversa, the thallus is much thicker, and the oogonia 

 larger and more erect, whilst the oospores are smaller and consequently do not fill 

 the cavity of their case. These differences are, except the last, simply differences 

 in size, and seem to me to depend simply upon circumstances of growth. The rela- 

 tively smaller size of the spore is a very frail hook indeed to hang a species upon. 

 The plant grows in springs and actively running water abundantly in this neigh- 

 borhood ; also on very wet ground, especially on that which is habitually overflowed, 

 such as the face of dams, neighborhood of springs, &c. In the water, it is frequently 

 on the ground, but also often clothes such objects as stones, largish sticks, &c. 



ORDER Neinatopliycere. 



Algae mnlticelnllarea, chlorophyllosoe, metnbranacote vel filamentosse, ramiflcatione ant instruct* 

 aut destitute. Propogatio fit aut ooaporis aut zoogonidiis, scd nunqunnt cnnjugationc. 



