FOEM OF THE TASCULAK FASCICULI IS BKITISII FEEXS. 83 



That this is an advantage, and is one great end gained by reciprocal 

 dimorphism, I can entertain no doubt. That in some cases this 

 dimorphism may be a step towards a complete separation of the 

 sexes, I wiU not dispute ; but good reasons could be assigned 

 to show that there is uo necessary connexion between reciprocal 

 dimorphism and a tendency to dioecious structure. Although good 

 is gained by the inevitable crossing of the dimorphic flowers, yet 

 numerous other analogous facts lead me to conclude that some 

 other quite unknown law of nature is here dimly indicated to us. 



On the Form of the Vascular Fasciculi in certain British Ferns. 

 By AaiHiTE H. Chuech, B.A. Oxon. Communicated by 

 W. Feancis, Ph.D., F.L.S. 



[Bead Dec. 18, 1862.] 



The distribution of the vascular tissues in the stem and stipes of 

 the British species of Ferns has been made the subject of much in- 

 teresting and accurate study by Dr. Ogilvie*. His papers are to 

 be found in the ' Annals and Magazine of Natural History ' for 

 December 1859 and November 1860. My own long-continued 

 examination of the living plants has not enabled me to detect any 

 but the most trivial mistakes in these full and admirable memoirs. 

 I have therefore only to propose a few slight alterations in Dr. 

 Ogihie's conclusions, and to make one or two additional remarks 

 on certain species and varieties which he omits to notice. The 

 present communication may be deemed the first instalment of 

 such supplementary observations. I may also here state that I 



* The following list of papers includes nearly all those in which the vascular 

 tissues of Ferns have been discussed : — 



Presl. Tentamen Pteridographise. Pragse : 1836. 



Ff?e. Die Gefassbiindel im Stipes der Fame. Praga; : 1847. 



OgUyie, Dr. Ann. & Mag. Nat. Hist. 1859 and 1860. 



Duval-Joure, J. Etudes sur le Petiole des Fougferes. In BUlot's Archives 



de la Flore de France ; pp. 57 & 149. 

 King. On Sigillaria. Edinburgh PhU. Trans. 1844. 

 Leighton, Eev. W. A. Hints on a new character in Ferns. Phyt. n. s. i. 



p. 256. 

 Moore, T. The Tascular Bundles of the Stipes of Ferns. Phyt. n. s. i. p. 378. 

 Eeicbardt, H. W. tJeber der Gefassbiindel Vertheilung im Stammc und 



Stipes der Fame. Denksehriften der Kaiserlichcn Akademie der Wissen- 



schaften, xvii'" Band. Wien : 1859. 



