INTRODUCTION TO CEYPTOGAMIC BOTANY. 223 



during the whole period of its existence, should increase in a 

 different way, the one from below, upwards, according as the 

 roots increase,* while Lessonia increases from above, down- 

 wards, as the leaves increase. The latter, therefore, is in 

 another respect analogous to Exogens.-j- 



207. As increase in Lessonia takes place by the constant 

 division of a flat leaf, the basal portion of which becomes the 

 petiole, and ultimately swells into a branch, the stems have 

 always a more or less elliptic form, and their section exhibits 

 an elliptic core. This form of the core is not, however, pecu- 

 liar, but exists equally in many other Algae. It is probable 

 that Lessonice, though attaining so large a size, are really of 

 very rapid growth. 



208. Macrocystis, which occurs imder a large number of 

 modifications, forms, like the LaminaricB of northern climes, 

 the outer belt of vegetation, and seems incapable of flourishing 

 without a depth of some six fathoms. A slender stem pro- 

 ceeds from a branched root, as in other LamiTiariw, bearing 

 at its tip a lanceolate or oblongo-lanceolate frond. This 

 divides at the base, the fissure extending upwards, so as to 

 form two petioles, each of which swells into an oblong or pyri- 

 form cyst. Another fissure is formed in a similar way a little 

 above, and so on, till a single frond may at the same time 

 have eight or ten fissures, each of which will loltimately gain 

 the common apex. The margins of the fissures are at first 

 perfectly even, but they soon become ciliate like the outer 

 edge. The continuity with the base is ultimately broken, and, 

 the division going on indefinitely, the whole reaches a length of 

 hundreds of feet, forming enormous masses, which are wafted 

 about by the waves. The most singular fact is, that fructifi- 



* Mr. G. H. Hofifman has, at my request, examined fresh specimens 

 of Laminaria digitata, and confirms Schultz's account in every essen- 

 tial point. I have had no opportunity of observing for myself since 

 the publication of Schultz's paper. 



f EcMonia buccincUis exhibits similar rings of growth, with an orbi- 

 cular central pith, as appears from an original drawing, by Dr. Hooker, 

 now before me. In Lessonia Sinclairii, from California, though the 

 stem is cylindrical, the pith is elliptic. 



