372 Johnson : Development of Saururus cernuus L 



Nymphaeaceae, as well as in many parasitic genera, of various fami- 

 lies, and much of the nucellar tissue remains also as perisperm in 

 certain of the Chenopodiaceae, Caryophyllaceae, and in the Canna- 

 ceae among the Monocotyledoneae. All of these facts seem to 

 me to show that Saururus is not among the higher Dicotyledoneae, 

 but for the support of the view that it is among the very lowest, 

 we must rely entirely upon a single character, namely, the absence 



of the floral envelopes. 



Finally the behavior of the endosperm at germination is 

 unique so far as I have been able to learn from the literature. We 

 may best regard it perhaps as the lower member of a series of 

 which such seeds as those of Phaseolus and Cncurbita form the 

 other extreme. In other words, in seeds of the latter type, the 

 endosperm completes its function of absorbing the tissue of the 

 nucellus, and passing this on to the embryo, during the ripening 

 of the seed, while in Saururus the final result is the same, but is 

 only reached during the germination of the seed. 



, Explanation of Plate 23 



Abbreviations used. ant, antipodal ; cot, cotyledon ; cp, carpel ; des, degenerat- 

 ing embryo -sac mother cell ; ea, egg apparatus ; eg, oosphere ; em, embryo ; ep, endo- 

 sperm ; epn, endosperm nucleus ; es, embryo-sac mother cell ; in, integument ; iin, 

 inner integument ; nc, nucellus ; oin, outer integument ; ov, ovule ; psp, perisperm ; sg, 

 ^ynergid ; st, stigma ; tp, tapetal cell ; vb, vascular bundle. 



1. Longitudinal section of ovule with mature embryo-sac, X 2 5°- 



2. Transverse section of carpel near the base, showing two ovules. The dotted 

 lines indicate the line of fusion of the edges of the carpel figured and of this with the 



adjacent carpels, X S°- 



3. Tip of nucellus with tapetal cells, one functional and two degenerating embryo- 

 sac mother cells, X 775- 



4. Longitudinal section of carpel showing two ovules, one with flask- shaped em- 

 bryo-sac, X 5°« 



5. Longitudinal section of embryo-sac slightly older than the last, X l S°* 



6. Longitudinal section of ripe fruit, showing degree of development of embryo, 

 endosperm, perisperm, integuments and carpel, X 4°- 



7. Longitudinal section of sprouting seed, showing pushing out of endosperm and 

 renewed development of embryo, X 3°- 



8. Part of longitudinal section of sprouting seed, showing embryo attached by 

 cotyledons to endosperm, X 3°- 



9. A twenty-day old seedling, showing relation of cotyledons, endosperm, seed 



coats and carpel, X 7- 



10. longitudinal section of the seed and cotyledons of such a seedling showing 

 the encroachment of the endosperm upon the perisperm, X H- 



