1889.] BOTANICAL GAZETTE. 3 1 



On Cuscuta Gronovii. 



HENRIETTA E. HOOKER, PH.D. 



(WITH PLATE VIII.) 



For a parasite that is parasitic from its heart and with all 

 its heart, after having tried an honest life, there is perhaps 

 no better example than doddor, which in our region (S. Had- 

 ley, Mass.) is Cuscuta Gronovii. We find it in abundance 

 in autumn, early and late, twining its orange-colored stems 



about grass, solidago, alder, and the like, with a glory of 

 white, bell-shaped flowers, in cymose clusters, appearing as 

 lateral buds in the axils of bracts. 



In preparing for the study of Cuscuta, fresh plants were 

 placed in alcohol, some were dried — as gathered on the host 

 and seeds were sowed in pots. From the first, imbedded in 

 celloidin, slides were prepared. The dried specimens vielded 

 knowledge of external parts and abundance of seeds, which 

 were valuable in ways that will appear later. The seeds are 

 exalbuminous, of comparatively large size, with a conspicu- 

 ous hilum and hard testa; but the latter yielded readily to 

 soaking in dilute potash, and careful di >ecting removed the 

 two coats and freed the coiled, snake-like embryo (fig. i). 

 The root end of the embryo lies outermost, and is slightly 

 enlarged, more noticeablv so after germination, when it evi- 

 dently remains, for some time, a store-house of nourishment. 



The time required for germination was found to vary 

 much. Some of the autumn-gathered seeds erminated in 

 three days, after a few days' soaking; others, obtained from 

 alder twigs out of doors, in February, and sowed drv, were 

 three weeks in showing si<nis of life. The end of the stem 

 which first emerged from the seed-coats was very soon cov- 

 ered with numerous short rhizoids, and careful observations 

 failed to discover any trace of a root-cap. Figs. 2 and 3 

 illustrate seedling dodders. The tip produces, even at a 

 very early stage, the rhizoids mentioned. Comparing fig. 3 

 with tig. 1, it will be seen that the root-hairs must have 

 grown very rapidly, none being on the embryo, just before 

 germination. Fig. 2 is the root end of a seedling 2 inches 

 long, and hence the rhizoids are much further develop* d. Fig. 

 5 illustrates one of the most interesting things in my study ot 

 the plant, and one that I could not find mentioned by any 



1 



