MORPHOLOGICAL DEVEL DPMEXT. 



integration stili more advanced: not simply inasmuch as 

 they unite much greater numbers of morphological units 

 into continuous masses; but also inasmuch as they com 

 bine the pseudo-foliar structure with the pseud-axial struc 

 ture. Our own shores furnish an instance of this in the 

 common Laminaria ; and certain gigantic Fuoi of the 

 Antartic seas, supply yet better instances. In some of 

 these, the germ develops a very long slender stem, which 

 eventually expands into a large bladder-like or cylindrical 

 air-vessel ; and from the surface of this there grow out 

 numerous leaf-shaped expansions. Another kind, Lessonia 

 fitscescens, Fig. 37, shows us a massive stem growing up 

 through water many feet deep a stem which, 

 bifurcating as it approaches the surface, flat 

 tens out the ends of its subdivisions into fronds 

 like ribands. These, however, are not true 

 foliar appendages, since they are merely ex 

 panded continuations of the stem. The whole 

 plant, great as is its size, and made up though 

 it seems to be of many groups of mor 

 phological units, united into a compound 

 group by their marked subordination to a 

 connecting mass, is nevertheless a single 

 thallus. The aggregate is still an aggregate 

 of the second order. 

 But among certain of the highest Algw, we do find some 

 thing more f han this union of the pseud-axial with the 

 pseudo-foliar structure. In addition to pseud-axes of 

 comparative complexity ; and in addition to pseudo-folia 

 that are like leaves, not only in their general shapes, but 

 in having mid-ribs and even veins ; there are the be 

 ginnings of a higher stage of integration. Figs. 38, 39, 

 and 40, show some of the steps. In Rhodymcma palmata, 

 Fig. 38, the parent-frond is comparatively irregular in shape, 

 and without a mid- rib ; and along with this very imperfect 

 integration, we see that the secondary fronds growing from 



