97 



N 



^ 



of germination in Polygonum Bistorta, and evidently, also, 

 P. viviparum, further Anemone alpina and 4- narcissiflora, 

 while in some species of Dcntaria, CJicErophylliim bnlbosum, 

 Ej^anthis hiemalis and Aconitum A/it/iora, the plumule does 

 not attain any further development the first year, but grows 

 out during the next year after the cotyledons and the cotylc- 

 donar tube have faded away entirely. Asa Gray has also 

 given some contributions in his paper : The germination of 

 the genus Megarrhiza, Torr,^ where he has described some 



germinating plantlets of M. Californica, and mentions the 

 same case as characteristic o{ Helphiniitm nndicaule. Further- 

 more Dicksont has observed, that Anemone eoronaria and 

 Podophyllnnt Eviodi germinate in the same manner, while 

 Lubbockj: has given some remarks upon Polygonum poly- 

 stachywn, of which the germination differs a little from the 

 above mentioned, as the plumule does not break through the 

 base of the cotyledonar tube, but passes through it, so that 

 the seedling has the appearance of possessing an erect 

 hypocotyl with nearly sessile cotyledons. Figs. 79 and 80, 

 on Plate XI, represent two germinating plantlets of Rheum 

 Moorcroftiamim which were cultivated in the U. S. 



s 



Botanical Garden, and that showed the same fact mentioned 

 above, that the petioles oi the cotyledons form a long tube, 

 and where the plumule becomes visible through a slit at the 

 base of it. Several specimens were examined, and this seems 

 to be the normal condition also of this plant. The tube was 

 cylindrical, and a transverse section showed the presence of 

 only four fibro-vascular bundles, while two groups of a collcn- 

 chymatic tissue were to be observed in the place where the 

 petioles had been united. Fig. 81 represents a section of 

 half of the tube. 



We have then seen that this manner of germination is the 



Silliman's Journal of Science, Vol. XIV, 1877. 



■f Dickson : On the Germitiation of Podophyllum Emodi. Transact, of 

 Bot. Soc. of Edinburc-h, Vol. XVI. 



t Sir John Lubbock: Phytobiological Observations, Journal of Liuu. 

 Society, VoL XXIV, No. 159, 1887. 



