336 Mr. J. Cleland on Vegetable Placentation. 



each of which is afterwards crowned with four or five more, and 

 thus, by repeated developmeuts, an umbellately ilabeniform, 

 fastigiate frond is formed! The space between each axil (or 

 each internode) invariably consists of a single cell, enlarging 

 upwards, and annulated in its lower half. The older branches 

 are thinly coated with calcareous matter ; the younger are mem- 

 branaceous. 



This plant is named in honour of Dr. James Apjohn, Pro- 

 fessor of Chemistry in the University of Dublin, and Mrs. Apjohn, 

 the latter of whom is a zealous collector and observer of British 

 Algae ; the former, I need not say, is worthy of any scientific 

 commemoration that may be offered to him. The genus belongs 

 to Valonie^e, and among Australian genera will stand nearest to 

 Struvea, Sond. ; but is much more closely related to the West 

 Indian ChamcRdoris, Mont., from which, however, it differs suffi- 

 ciently in habit and character. In aspect Apjohnia looks almost 

 like a very luxuriant and robust specimen of Cladophora pellu- 

 cida, though not very closely related to that plant. 



Melbourne, January 10, 1855. 



XXXI. — Some Remarks on Vegetable Placentation, 

 By John Cleland, Esq.* 



The object of the few following remarks is to bring forward some 

 evidence against the axile theory of placentation, and to show 

 that the free central placenta found in many plants is really 

 composed of a second whorl of carpels with everted edges. 



My observations are founded entirely on the Ld/chnis and Pri- 

 mula, In the latter we have the most perfect example of a free 

 placenta, while the former illustrates most distinctly the theory 

 which I wish to bring forward. 



On opening the fruit of the Lychnis dioica, its carpels are seen 

 to be united into a perfect circle, and to present no trace of their 

 homology with the leaf except in. the venation on their internal 

 surface. When the seeds are removed the funicular cords are 

 seen arranged in five vertical double rows with smooth spaces 

 between. On making a transverse section, these smooth spaces 

 are found to be composed of a pad of white cellular tissue, and 

 alternating with them and with the rows of cords are the five 

 rays of a star-shaped mass of the same white cellular substance 

 occupying the centre. This star seems clearly to indicate the 

 formation of the placenta from five parts, and the position of the 



* Read before the Botanical Society of Edinburgh, April 12, 1855. 



