The Morphology of Ruppia Maritima. 151 



and one can easih- see a small prominence (fig. 106, cot), accompanied 

 interiorly by a number of cell-divisions, which is obviously the be- 

 ginning of the cot}'ledon. Moreover, at its right is another markedly 

 meristematic region, the future stem apex or epicot3'l (fig. 106, st). 

 Wille's description of the subsequent development up to the 

 mature embryo agrees essentiall}' with m}" slides, so that I confirm 

 his observations in the main, adding a few details. For the sake 

 of clearness, each mem.ber will be described separately. 



The Cotyledon. Originating as described above, the cotyledon elon- 

 gates and the epicotyl develops at its base. In the course of its growth, 

 the cotyledon develops basal sheaths similar to those characteristic of 

 the leaves of a mature plant, which then surround the epicotyl. 

 Concerning this condition Wille (1883, pp. 3, 4) says, " Hos den 

 modne Frugt er Plumulaen ganske omgiven af Cotyledonet (Tavl. 

 I, fig. 25), kun en trang Spalte f&rer ind til Hulen," but figures an 

 embryo with a large open hollow at the base of the cotyledon, 

 where the epicotyl ma}' be seen. As a matter of fact, in Ruppia 

 maritima at least, the cotyledonar}- sheaths overlap one another 

 for almost the whole of their length, essentially as do the sheaths 

 of the foliage leaves (PI. XV, fig. 118;. Only at the upper end of 

 these sheaths is there a small cleft remaining (Fig. 118, x) which 

 may be the " trang Spalte "' mentioned by Wille. Thus the sheaths 

 enclose the epicotyl so that it is quite shut off from view. In 

 PL XrV, fig. 112, and PI. XV, fig. 116 these sheaths appear in 

 section in not quite mature embryos, and figures 117 and 118 show 

 them in a cotyledon dissected from a mature embryo. It is inter- 

 esting to note that the axillary scales may be seen within the sheaths, 

 at their base, as in the mature plant. 



Wille (1883, PL I, fig. 25) figures the cotyledon as elevated a 

 considerable distance above the hypocotyl, although still extend- 

 ing more or less horizontallj', and one might conclude that pos- 

 sibly herein is a specific difference between Ruppia rostellata and 

 R. maritima, were it not for the fact that Irmisch (1858, fig. 37, 

 pi. I) figures the cotyledon closely appressed to the hypocotyl as 

 I find it in R. maritima (PI. XV, fig. 119). In Text-fig. 28, p. 152, 

 this horizontal position has been slightly disturbed through manip- 

 ulation. 



The Epicotyl. PL XIV, fig. 112 shows the epicotyl in a nearly 

 mature embr3-o. It consists alwa3's of a second leaf and the growing 

 point, the latter not appearing as prominentl}^ here as in other sections. 

 Wille (1883, p. 3, figs. 25 and 26) is in doubt whether this smaller pro- 



