634 



SCIUNGE 



[N. S. Vol. XXXI. No. 799 



The Origin of the Primary Bulb in Erythroniumr 



Frederick H. Blodgett. 



In the mature seed the embryo of Erythroniuni 

 is a globose mass of cells, without differentiation, 

 slightly pointed toward the mioropyle. The seed 

 remains dormant during the summer. The embryo 

 begins to elongate with the coming of the late 

 summer rains. The tip of the cotyledon is early 

 organized as a haustorium, and absorbs the reserve 

 cellulose along the line of elongation. When the 

 embryo has elongated to half the length of the 

 seed the stem apex may be recognized. 



The stem apex is located in a narrow transverse 

 slit situated just behind the radicle. By the 

 growth of the cotyledon above the slit, the radicle 

 and the stem apex are forced into the soil. The 

 hypocotyl takes no part in the descent of the stem 

 apex. With the exhaustion of the reserve food of 

 the seed the descent of the stem apex stops. The 

 primary root pushes forward from the end of the 

 descending axis, while the cotyledon frees its tip 

 from the seed coats and reaches upward into the 

 air. One root only is formed by the seedling, and 

 this is unbranched, in our species. 



A dropper (primary runner) is formed from the 

 walls of the slit and cells immediately adjacent, 

 and carries the stem apex (primary growing 

 point) forward from the base of the descending 

 axis as the terminal bud in the dropper. The 

 walls of the dropper are equivalent to the first 

 scale leaf of the primary growing point, fused 

 along one side to the stalk of the bud through 

 which vascular connection is maintained with the 

 cotyledon and primary root. The relation of 

 parts is similar to that of the raphe to the rest 

 of the ovule in anatropous ovules. 



The primary growing point within the dropper 

 sheath organizes a second scale leaf, the first scale 

 being the dropper sheath. 



The second scale leaf encloses the growing point, 

 and these form the bulk of the primary bulb; 

 the sheath of the dropper forms the husk about 

 the bulb. The starch for storage in the growing 

 bulb is obtained through the photosynthetic act- 

 ivity of the cotyledon, acting as the first foliage 

 leaf. The death of the other parts of the seedling 

 leaves the terminal bud of the dropper isolated in 

 the soil as the primary bulb, and marks the end 

 of the first vegetative period of the cycle from 

 seed to flower. 

 Some New Bylrids and their Bearing on the 



Classification of Wheat: B. C. BtnFFUM. 



The classification of wheat has gone through 

 several changes since the first division by Lin- 

 naeus into fall and spring species. Hackel recog- 



nizes three true species and two subspecies of 

 Triticum. 



Should some botanists of the present apply their 

 ideas of specific characters to cultivated plants 

 we should have many species of wheat. It is 

 doubtful if any term used in science means less to 

 the thoughtful student than the word species. 



My recent work with wheat shows that we may 

 accept the species of Hackel from the old stand- 

 point of their action in cross pollination and yet 

 all have the same origin. 



From a single hybridization between a mutating 

 Tritioum sativum (winter wheat) and a mutating 

 Triticum dicoccum ( winter emmer ) , I have se- 

 cured a complete breaking up of wheats into all 

 the species and types since the beginning of time, 

 and in addition produced infertile hybrids, mon- 

 strosities and new types not intermediates. The 

 second generation has given well-defined specimens 

 of Triticum monococcum, T. dicoccum; T. spelta, 

 T. polonicum and almost if not quite every well- 

 marked type of T. sativum, including various col- 

 ored bearded and beardless, square head, club and 

 long-headed forms, with every arrangement and 

 shape of glumes and spikelets. 



The evidence is conclusive that all wheats have 

 developed from not more than two and probably 

 from a single form. 



The question arises should we accept one species 

 or are we justified in using every variation as a 

 specific difference which would divide wheats into 

 many species, and if so, where may the line be 

 drawn ? 



The Closing Response of Bioncea muscipula Ellis; 



W. H. Brown and L. W. Sharp. 



The closing response of Dioncea depends upon 

 the intensity rather than upon the number of 

 stimuli, the number of stimuli required varying 

 in the inverse order of their intensity. 



Response is normally brought about by the com- 

 pression of certain cells at the bases of the sensi- 

 tive hairs, but the compression of other cells of 

 the blade also causes closure, and it is probable 

 that the latter cells are equally sensitive with 

 those at the bases of the hairs, as is indicated by 

 the effect of electrical and thermal stimulation. 



The closing response follows the application of 

 mechanical, electrical or thermal stimulation. It 

 also follows a combination of stimuli of two 

 kinds when consecutively applied, the individual 

 stimuli being of an int-ensity such that either 

 alone would be insufficient. 



The effect of mechanical stimulation is due to a 

 compression of cells, and not to contact with a 



