82 



frorrt below and the okl layer thrown off. Solms-Laubach speaks also in bis paper of the 

 growth in thickness of the cortical layer after the manner of Lithothamnion, whereby new 

 conceptacles can spring forth and old ones becoming overgrown, are submersed in the tissue 

 of the plant. Solms-Lai :rs rather briefly to the nodes, only saying that the node 



consists of two layers of cells and that the cortical layer falls off as a rule. 



The anatomical structure, first noted by Zanardini and afterwards mentioned by Schmitz 

 and H ii proved to be a character of great systematic value and I wil! therefore 



describe it at f uil length. 



In Arthrocardia, Cheilosporum, j'ania and Corallina the cells in the central strand of 

 each joint have the same dimension throughout the whole joint; each successive layer is as a 

 rule as long and as broad as the preceding or succeeding one. The cells stand in vertical rows 

 one above another; they may grow a little longer or shorter, the difference is a gradual one, 

 never an abrupt one. 



In Amphiroa the case is different; i, 2, 3, 4 or even more layers of long cells (articoli 

 Zan.) will alternate with a row of short cells (otricoli Zan.) marking a period of intra-nodal 

 growth; each joint may have several of these periocls of growth. The long cells in the successive 

 rows of one period of growth are not of exactly the same size ; as a rule the cells of the first 

 row are the longest, the cells of the succeeding ones becoming gradually a little shorter, but 

 the transition to the last row, the one with the short cells, is as a rule abrupt. The regularity 

 with which these rows of long and short cells alternate is liable to much variation in each 

 species and in each plant. Still a certain rule may be detected. Thus in the case of Amphiroa 

 fragilissima (L.) Lam., one of the many types of the genus, 4, 5 or 6 rows of long cells will 

 be foliowed by a row of short ones. This number of long-celled rows may be reduced to 2 

 or 3, or increase to 7 or 8, but by far the greater number of joints will have intra-nodal 

 periods of growth consisting of 4, 5 or 6 rows of long cells. In Amphiroa verrucosa Kütz. 

 we find very regularly one row of long cells alternating with one row of short cells and in 

 Amphiroa rigida Lam. two long ones alternating with a short one, but in the latter case the 

 alternation is not so regular as in A. verrucosa. 



Studying the nodes of other Amphiroae I found that the nodes of these plants do not 

 always consist of two rows of pericline cells, as is the case with the Amphiroae of the Gulf 

 of Naples desenbed by Solms-Laubach but that a great number of rows may take part in 

 their formation (PI. XV, fig. 5); the cortical layer of the node does not drop off but persists 

 in many species and even grows in thickness, and in one or two species the cortical layer 

 remains calcified and the node is only indicated by a zone of uncalcified rows in the central 

 strand (PI. XV, hg. 6). Almost startling is the wealth nature exhibits in producing such a 

 simple thing as a node of Amphiroa. But however different the ways of forming the node 

 may be, one thing is invariable and can be relied upon as a fixed rule: the cells in the 

 node have always the same dimension o r n e a r 1 y s o as the cells in t he 

 whole plant. The only exceptions which I have discovered to this rule are A. rigida and A. 

 verrucosa, the long cells of which have an inclination to grow longer still in the node; but 

 even here the differences are not great. 



