1908] Observations on Seedling Plants. 173 



the seed. The plumule is green and located in a furrow formed 

 by the large cotyledon, the margins of which tightly enclose the 

 plumule. The germination commences while the seed is still 

 floating upon the water, and the first sign of the young plant is 

 the plumule breaking out through the mucilaginous envelope and 

 separating itself from the clasping margins of the cotyledon; the 

 first leaf succeeding the cotyledon is exactly opposite this, and 

 represents merely an open sheath-like organ with two ribs. This 

 rudimentary leaf-structure may be frequently observed also 

 in the second and third leaf of the seedling, while in some seed- 

 lings I noticed that already the second leaf showed a distinct 

 petiole and a small elliptic blade. In regard to the root system, 

 the primary root does not develop, but secondary roots in pairs 

 appear at an earl}^ stage, and attain a considerable length, 

 though without ramif3dng. 



Orontium aquaticum, L. germinates in the same way, but the 

 plumule is here located in a shallow cavity of the cotyledon 

 without being surrounded by this. The first leaf succeeding the 

 cotyledon is terete, not bicarinate, and this form of foliage be- 

 comes repeated in several of the following leaves; the primary 

 root stays rudimentary, but soon becomes replaced by several 

 lateral. 



We have thus in monocotyledonous seedlings several 

 interesting types, in which quite a prominent variation is notice- 

 able in respect to the structure of the cotyledon, the first leaf 

 or leaves succeeding this, and the root system. In some of these 

 the seed is exalbuminous, and the cotyledon epigeic, as in 

 Alisnia; or we have the peculiar, globular cotyledon in the 

 exalbuminous seeds of the aquatic Orontium and Peltandra. 

 Epigeic is, furthermore, the cotyledon of Agave, but not until it 

 has absorbed the food-substances of the endosperm. The 

 hypogeic cotyledon is much more frequent, but varies in regard 

 to the structure of the absorbing portion, for instance, if we 

 compare the scutellum of the Graminece with the club-shaped 

 cotyledon of Cyperacecs, Smilax, Commelma, Ariscenia, etc. 

 Sometimes the cotyledon possesses a distinct sheath which 

 envelopes the plumule, as in Arises ma, Smilax and Agave; if the 

 coleoptile of the Gramine(B and Cyperacece might prove to re- 

 present the sheath of the cotyledon, this would then frequently 

 appear at some distance above the scutellum, separated from 

 this by an internode or node, according to some authors. The 

 cotyledon may subtend a bud as in Smilax, and we remember 

 that in several GraminecB a bud has been observed in the axil 

 of the coleoptile, whether this be an independent leaf or merely 

 a part of the cotyledon. The foliage of these seedlings is, also, 

 characteristic; for instance, the epiblast and coleoptile in 



