128 



proper conditions the seed absorbs water and the embryo lengthens by 

 growth both above and below the plumule. The growth of the cotyledon- 

 ary petiole is more rapid than that of the radicle, so that the radicle, 

 with the i)lumu]e, is soon pushed outside the seed coat. The cotyle- 

 donary petiole reacts to the stimulus of gravity so that the radicle is soon 

 directed downward. Fig. 2. The one cotyledon remains inside the seed as 

 an absorbing agent. Fig. 4. The i-adicle grows down rapidly to form a 

 primary root. Later one or two other roots may be formed. Immediately 

 after the establishment of a root system or water absorbing system, the 

 portion just below the plumule becomes enlarged by the storage of food 

 stuff transferred from the endosperm of the old seed. Figs. 3 and 4. 



In case the germination is complete, the formation of a root system is 

 followed l>y the growth of the single simple leaf up from the plumule, 

 through the cotyletlonary petiole to the light, Fig. 0. Usually, however, 

 only scales are formed around the l)ud. In either case, when the food 

 material has been absorbed, the tissues connecting seed and seedling 

 shx'ivel up, leaving the young plant indeitendcnt. After a period of about 

 eight weeks from the beginning of germination the corms will be found 

 free from the seed and with the roots detached and broken down, all 

 ready for a period of rest, Fig. 5. 



It may be of interest to note that I. hntrontiii m gives utlier i-vidence 

 of Incomplete response to seasonal changi-s. iMniiig the sunnuer of 1913 

 the rorms of a considerable colony weic dug up lor experimental pur- 

 po.ses. Although these corms were scattered in the soil but a few inches 

 apart, and some had shown very vigorous growth of stem and leaves, 

 about half of them had made no start toward growth. The conditions 

 were certainly the same for all individuals of the colony, and were good, 

 as shown by the growth just mentioned. Whether this jilaut is subject 

 to definite periodicity retpiiring more than the usual rest season, or is 

 controlled by some as yet unconsidered influence, can oidy be left a 

 question. 



