240 W. HOFMEISTEB ON THE DEVELOPMENT 'OF ZOSTERA. 



branch. In Zostera marina, when the formation of flowers 

 commences, both the previously inert axillary buds and also the 

 terminal shoot of the little-branched or even simple sterile plants, 

 become converted into inflorescences. In Zostera minor the rule 

 is for axillary sprouts standing far back from the sterile terminal 

 shoot, to become transformed into blossoms. This distinction 

 between the two species, so striking at first sight, appears to 

 depend principally upon the fact that in Zostera marina the old 

 portions of the stem die away rapidly, within a few months, 

 from behind forwards, while in Zostera minor they persist for 

 more than a year. 



When the terminal bud of a plant of Zostera marina enters 

 upon a transformation into a spadix, the ordinary series of 

 linear stem- leaves with sheathing bases (having the divergence |), 

 becomes interrupted by a cylindrical leaf-sheath, devoid of 

 any indication of a lamina, the two lateral borders of which 

 sheath, enclosing the terminal bud, adhere firmly together. The 

 axillary sprouts which become blossoms arise with a similar 

 sheath. The next internode of the flowering sprout bears a leaf 

 like the stem-leaves (laub- blatter), but with a comparatively shorter 

 lamina, which, like the leaves of the Zostera generally, has a 

 divergence of \ from the leaf next older than itself. The 

 sheathing base of this leaf envelopes the inflorescence, i. e. the 

 expanded, flat, long-protracted end of the stem, that surface of 

 which turned away from the last leaf bears the anthers and 

 ovaries. 



From the axil of the sheathing bract (vorblatt) of the fertile 

 sprout (PI. VI. fig. 1 a] arises a shoot, resembling in all respects 

 its parent sprout, with which it is coalescent for a considerable 

 distance (fig. 1 b). At the place where the cohesion ceases the 

 new sprout bears its first, sheathing leaf (fig. 1 b 1 ). This 

 diverges J of the circumference of the stem from the bract 

 (vorblatt} of the sprout of the preceding rank, and is parallel 

 with the stem-leaf (laub-blatt) in the axil of which that arises. 

 The sheathing leaf is succeeded by a stem-leaf (laub-blatt) 

 (fig. 1 b 2 ), above which the sprout terminates with the inflores- 

 cence (fig. 1 b). The axil of its lowest, sheathing leaf sends out 

 a fructifying branch of a new rank (fig. 1 c), and so on, till the 

 exhaustion of the growing power of the blossoming plant, in 



