1908] Observations on Seedling Plants. 169 



developed in the axil of the cotyledon, and that this bud develops 

 into a small tuber (B in Fig. 7). So far as concerns the structure 

 of the cotyledon, its apex and short sheath, this type of seedling 

 is common to many, Liliacece. Amaryllidece. PalmcB, Dioscoreacece, 

 IridecB, etc. 



A fourth type is characteristic of CommelinacecB, and it differs 

 from the former by the prolongation of the free part of the 

 cotyledon, which here represents a long, filiform organ between the 

 apex and the sheath; moreover, the primary root is surrounded 

 by a sheath, the so-called coleorhiza, which it has to penetrate. 



These four types thus illustrate the most frequent structure 

 of seedlings of Monocotyledones ex-cl., CyperacecB and GraminecB, 

 and the principal distinction consists in the position of the 

 cotyledon, being epigeic or hypogeic ; moreover, in the varied 

 development of the cotyledonary sheath. In regard to the 

 hypocotyl we have seen this to be well differentiated in Smilax, 

 while it is either obsolete or undeveloped in the others. The 

 primary root may persist for a longer or shorter period, but the 

 most important character derived from this organ is the presence 

 of a coleorhiza as observed in Commelina. 



A feature common to these types is, however, that the root 

 is the first organ to appear when the seed germinates; then 

 follows the cotyledonary sheath, and finally the first leaf of the 

 plumule. In this respect the Cyperacecc make a notable exception 

 from all the other Monocotyledones with perfect embryos. We 

 might examine Cy penis vegeUisy^iWd., as an example of this type 

 of germination, illustrated on Plate IV, Figs 8 and 11. 



When the seed germinates (Fig. 9) the plumule surrounded 

 by the coleoptile is the first to appear, pushing out through 

 the opened base of the achene, and carrying with it the small 

 root, merelv visible as a minute wart. If we remove the cotyledon 

 from the seed (Fig. 10), we notice the very simple structure of the 

 embryo: the large clavate cotyledon, the sheath of which 

 (coleoptile) covers the plumule completely, and finall5' the small 

 root with a wreath of hairs. All these organs are, also, readily to 

 be observed in the still younger embryo (Fig. 8) just before germ- 

 ination. The further development of these organs may be 

 observed in Fig. 1 1 , where the root has commenced to grow out, 

 and where the coleoptile has attained its final shape : as a tubular 

 leaf with a small, blade-like apex ; no such advanced development 

 of the coleoptile was observed in the other types described above. 

 In the CyperacecE the coleoptile thus develops into a long sheath 

 raised high above the plumule, and it turns its back toward the 

 absorbing portion of the cotyledon. Sometimes, as for instance 

 in Fuirena squarrosa, Michx., a long stem-like organ develops 

 between the coleoptile and the enclosed portion of the cotyledon, 



