98 . 



normal one in several plants, especially in some Ranun- 

 culacec-e, Berberide^x, UmbelliferiE, and Polygonace.ne, while it 

 may occasionally occur as an abnormal condition in some 

 others, as for instance in Ricinus, where it has been observed 



by Magnus.* 



If we now turn to the germination of Iponiaea paniculata 

 (Plate XI, Fig. 76), we see that the plumule is there situated 

 at the summit of a large root, and between two very long- * 

 petioled cotyledons, just as it has been observed, for example, 



r 



in several Um^bellifercX. It is relatively the same case, as ^ 



observed in Delphinium nudicaiile^ Avith the exception that v^^ 

 the petioles are free, while the plumule, notwithstanding 

 that it is protected in the same manner, is kept well under- 

 ground and protected against severe cold and draught. This 

 occurrence in some species of Ipomoea has been mentioned 

 by Gray in his '' Notulae exiguae,*' t where he has described 

 the same manner of germination in /. leptopliylla, L pan- 

 durata and L Jalapa, all of which are large-rooted species. 

 There was, however, one germinating plantlet of /. panicu- 

 lata (Fig. "jj^ which showed four cotyledons, of which two 

 were grown together with their petioles and blades, whereas 

 the other pair were perfectly free. The plumule was situated 

 close to the base of the furrow, formed by the connate petioles 

 (Fig. 78), and this fact might lead to the conclusion, that 



the cotyledonar tube probably has existed or still exists also 

 in this genus. 



In contrast to these cases, where the plumule is kept 

 underground, or at least close to its surface, we have seen, 

 in most of the other dicotyledoneous seedlings examined, 

 that a distinct hypocotyl has been developed. This might 

 seem to be rather injurious to the plant, as the plumule does 

 not receive any further protection, and the hypocotyl is 

 ordinarily not strongly developed, is neither thick nor pos- 

 sesses any mechanical tissue. But it must then be remem- 



* P. Magnus : Ueber zwei monstrose Keimpflanzeii von Riciniis, 

 Verhandl. d. Bot. Vereins d, Provinz Brandenburg. Vol. XVIII, p. 107. 



t Botanical^ Gazette, Vol. V, p. 87, 1880. 



