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A TEXTBOOK OF THEORETICAL BOTANY 



produce any outgrowths but exceptionally it produces endogenous 

 adventitious roots (see the account of the Podostemaceae, below). In 

 Cinnamomum the dwarf hypocotyl produces even the primary radicle 



Fig. 1443. — Raphanus sativus. Radish. Development of the 

 swollen hypocotyl. {After Troll.) 



endogenously, an almost unique case in the Dicotyledons, though found 

 commonly in the higher Monocotyledons. Adventitious buds are not un- 

 common on the hypocotyl of Euphorbia lath vr us. 



There are a number of departures from the usual paired cotyledons in 

 Dicotyledons. Several genera regularly produce more than two, for 

 example Bruguiera (Rhizophoraceae) has four, and Persoonia (Proteaceae) 

 three or four. Eranthis frequently has three. Splitting of the cotyledons 

 (schizocotyly) occurs in varying degrees as an anomaly in many seedlings 

 of different families, all stages between simple emargination and complete 

 fission being found. Everything points to the two-cotyledonary state as 

 primitive and to the supplementary cotyledons being formed by the 

 splitting of one or of both of them. Hill and de Fraine considered that 

 this is true also of the polycotylous seedlings of Coniferales. The opposite 

 condition or syncotyly occurs in a great number of dicotyledonous seedlings 

 and like schizocotyly it occurs in all degrees of completeness. In endo- 

 spermic seeds the union is generally symmetrical, by both edges, forming 

 a cotyledonary tube, while in non-endospermic seeds {i.e., with storage 

 cotyledons) the union is generally lateral, by one edge only, the differences 

 being due to space and symmetry relationships within the seeds. A number 

 of genera, especially in Ranunculaceae, have normally only one cotyledon 

 and are therefore classed as pseudo-monocotyledonous. We shall discuss 

 them later in relation to the origin of the Monocotyledons as a class. 



