KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 25. N:0 5. 93 



14. M. furcata, Kales (Br. Desm. p. 73, t. IX, f. 2, non Agardh; Wallich Beng. Desra. 

 j). 280, ex p.; Micrasterias melitensis Ralfs Ann. N. H. vol. XIV, p. 260, t. VI, f. 2, 

 non Mengh.; M. crux-mélitensis var. b furcata Rabii. Fl. Eur. Alg. III, p. 190; M. 

 radiata Hass. Br. Fr. Alg. p. 386, t. XC, f. 2; M. melitensis fi gracilis, Kutz. Spec. 

 Alg. p. 171). Hse formas tres: 

 Forma « typica. Fere ut in Ralfs 1. c; lobulis lateralibus apice forcipatis. 



/? gracillima. Lobis attenuatis; apicibus lobuloruni dentatis; lobo polari paullo 



exserto. 

 / expansa. Major; radians; apicibus lobuloruni sub-bicuspidatis. 

 T. V, f. 5. Dimensiones: 





Long. 



lat. 



lat. isth. 



lat. apic. 



lat. lol). pol. 





C( 



145—150 



124—130 



20 



48 



22 ,u 



f. 5 a 



l* 



135 



120 



24 



70 



22 » 



» » b 



r 



165—176 



140—158 



22 



86 



27 » 



» » c 



Hab. fi Bengal; « and y Northern India. 



[Söte. Of this species Wallich, 1. c. p. 280, says »abnndant and occurs in every 

 state intermediate between the typical one and its variety commonly described under 

 the specific naine of M. cruas-rnelitemis». From Dr. Wallichs remarks upon these 

 and other forms, and also upon »divergence» and specific limits (pp. 184 — 5, 275, 

 277, etc.) it appears that between 1854 and 1860 he bad become an enthusiastic evo- 

 lutionist, and as such was much inclined to believe that consimilar forms were most 

 probably oriyinaUy eognate. Against this view W. Archer advanced arguments (Dubl. 

 N. H. Soc. Träns. 1865) urging the persistence of type, i. e. of species, in the Des- 

 midieaj. Both against and for the fusion of species there is much to be said; the 

 qucestio vexata will hardly be settled, as Evolution demands generations of forms upon 

 which to effect change, which would require generations of observers to detect and 

 consider. For my own part I express no opinion upon the controversy, except that, 

 as all my figures of the two preceding species (except f. 4 Ii) are ad nat., the truth- 

 fulness of Dr. Wallichs remarks upon diversity of form is amply sustained.] 

 15. M. alata, Wallich (Desm. Beng. \). 279, t. XIII, f. 11, 1860; Lagerh. Desm. Beng. 

 p. 5; M. ala-draconis Wall. Mscr. No. 78, 79). Forma' duae: 

 « typica. Semicellula' sub-7-lobata'; lobis radiantibus, expansis. 

 fi depressa. Lobis lateralibus curtis, depressis; lobo polari magis exserto. 



Dimensiones: 



lat. isth. It. apic. It. lob.pol. crass. 



14—20 60—66 12.5 28 «. T. VI, f. 3, 5. 





Long. 



lat. 



« typica 



160—174 



148—154 



Wallich 1. c 



147 



142 



fi depressa 



152 



125 



15 50 14.5 — T. VI, f. 2. 



Baboosole, 22 Oct. 55, G. C. W. 



The zygospore of this species was first described by Lagekheim (Amer. Desmfl. 

 p. 231, t. XXVII, f. 5), bis figure seems to possess rather fewer and thicker spines 

 than the one I noticed. The dimensions given by Lagerh. are Diam. c. acul. 98, ' 

 s. acul. 58 ,u; mine (f. 4) give Diam. c. acul. 100, s. acul. 60 ju; thus the}- practically 



