. The Canadian field-naturalist. 16 The Canadian Field-Naturalist [Vol. 71 The mature plant multiplies by producing a series of buds at the bottom of a pouch at the apical extremity of its frond (at right in Fig. 5). As described by Lawalree, each bud arises from a single cell of the dermatogen and soon develops into an elongated pro- tuberance. Several vegetative generations of buds may be found in any free-floating plant and each generation may be repiresented by more than one bud. The sequence of budding may be briefly described from Fig. 5. The in the adult. The top-to-bottom differentia-
. The Canadian field-naturalist. 16 The Canadian Field-Naturalist [Vol. 71 The mature plant multiplies by producing a series of buds at the bottom of a pouch at the apical extremity of its frond (at right in Fig. 5). As described by Lawalree, each bud arises from a single cell of the dermatogen and soon develops into an elongated pro- tuberance. Several vegetative generations of buds may be found in any free-floating plant and each generation may be repiresented by more than one bud. The sequence of budding may be briefly described from Fig. 5. The in the adult. The top-to-bottom differentia- tion of its tissue is clearly visible. Pre- sumably this differentiation is influenced by gravity and all buds show the same polarity vsfith respect to this differentiation. On the contrary, successive generations show re- versed polarity in the matter of apical differentiation. The apex of bud lie is op- posite the apex of its parent, I. The reason for this is unknown, but can give rise to some interesting J Fig. 5. Photomicrograph of longitudinal section of plant of Wolffia punctata (X8S). For description see text. (R. J. Moore) adult frond is indicated at I, and successive vegetative generations are indicated at II and III. The buds within each generation are marked by the letters a, b, c, etc. in order of their development. The largest bud present in this case is labelled lie. This bud will shortly be liberated by the rupture of the stalk at its lower left corner. The ruptured stalks of two earlier buds of the same generation, lla and lib, are visible. A later bud of this generation is marked lid. Each bud of this generation is capable of pro- ducing buds of the third generation, and one borne by bud lie is indicated as IIIc. A very early third generation bud can be seen on bud lid on its lower left side. It will be noticed that bud lie, the most mature bud, already shows internal structure well on its way to the differentiation found REFERENCES Fletcher, J. 1
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