290 SUMMARY OF CUEEENT RESEARCHES RELATING TO 



are sinking in the "n'ater, or when canght by the paraphyses of the 

 barren conceptacles. 



The oospores displayed evidences of germination after nineteen 

 hours, putting out a colonrless rhizoid. Excluding this, the young 

 plant is not larger than the oospore. 



Embryo Plantlets of Fucus.*— Dr. W. E. M'l^ab calls attention 

 to young embryo plants of Fucus vesicuhsus, adhering in considerable 

 numbers to the conceptacular region of the thallus. They probably 

 escape from the thallus after a short adherence. 



Durvillaea Harveyi.f — Herr J, Grabendorfer describes in detail 

 the structure of this alga from South Brazil, belonging to the Fucaceae, 

 from dried specimens and material preserved in alcohol. 



The most important point brought out in the structure of the 

 vegetative organs is the absence of an apical growing point such as 

 appears to exist in all other Fucaceae, with the exception perhaps of 

 SjjlacTinidimn. 



The conceptacles agree in all important points with those of 

 Fucus, but are considerably smaller ; DurviUsea is dioecious ; but no 

 difference is perceptible in the mode of growth of plants of the two 

 sexes. One point of difference from Fucus was established, that the 

 contents of the oogonia divide, not into eight, but into four oospheres : 

 viz. first of all into three by two transverse septa, and then the 

 middle one of these again into two by a longitudinal wall. 



Lessonia ovata.^ — This seaweed from South Brazil, belonging to 

 the Laminariacese, has been subjected to a critical examination by 

 Herr J. Grabendorfer, both in dried specimens and in material 

 preserved in alcohol. 



In the structure of the vegetative organs Lessonia shows no very 

 marked departure from other genera of the order. It agrees with 

 Macrocystis rather than with Laminaria in showing a rather marked 

 differentiation between the medullary and the cortical tissues in the 

 stem. The " sorus " consists of two kinds of cells peculiar to it : — 

 (1) the sporangia, ovate cells filled with numerous polyhedral bodies, 

 and at first thin membrane ; and (2) the paraphyses, club-shaped 

 cells with moderately thick membrane and brown contents. Both 

 paraphyses and sporangia are foi-med from epidermal cells, 



"ProtliaUus" of Padiiia.§ — Dr. G.M. Giles describes a structure 

 which he regards as the " prothallus " or sexual generation of Padina 

 pavonia, found abundantly on the fronds of the seaweed itself 

 on the coast of British Burmah. They are minute flat bodies, on 

 which were observed peculiar structures which the author considers 

 to be of the nature of antheiidia and archegonia. Young fronds of 

 the non-sexual form were found sprouting from the edge of these 

 prothalloid bodies. 



* Ann. and Mag. Nat. Hist., xvii. (1886) pp. 163-4. 

 t Bot. Ztg., xliii. (1885) pp. 609-18, 625-36 (1 pi.), 

 t Ibid., pp. 641-8, 657-64 (1 pi.). 

 § Joum. Asiatic Soc. Bengal, liv. (1885) pp. 71-5 (2 pis.). 



