586 THE STRUCTURE OF ECONOMIC PLANTS 



carpels may attain varying degrees of development, occasionally 

 forming a mature pistil so that a perfect flower results. 



As the stamens are developing, the calyx and corolla lobes arise 

 from the margin of the perianth tube in a spiral arrangement and 

 the broad thin corolla lobes overarch the androecium. Large 

 intercellular spaces develop in the parenchymatous tissue of the 

 perianth tube, and these schizo-lysigenous cavities finally extend 

 from near its base to the point of divergence of the corolla. 



The morphological interpretation of the dissimilar stamens 

 which constitute the androecium of some of the cucurbits has 

 been a controversial matter. Heimlich (i6) has supported the 



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Fig. 306. Development of androecium ; the single stamen is to right in each figure, while 

 behind and to left are two double double ones. (From Sachs, after Payer, Textbook of Botany, 

 Clarendon Press.) 



original interpretation of Naudin (30) that the two bilocular 

 stamens are complete; and that, in the third, one locule fails to 

 develop. Miller (xS), comparing Echinocystis with other genera, 

 has concluded that the bisporangiate, unilocular stamen is a 

 complete one and not a "half organ" in the developmental sense. 

 On this basis, he regards Cucumis and Cucurbita as having "five 

 stamens, four of which are united in two masses," and agrees 

 with Eichler (8) and van Tieghem (36), who regarded the tetra- 

 sporangiate, bilocular stamen as a double organ. Miller based 

 his interpretation upon the observation that the tetrasporangiate 

 stamen in Echinocystis arises from two separate primordia which 

 form a single structure owing to lateral coalescence and the growth 

 of intervening tissue between the original primordia. 



A peculiarity of the pollen tube has been observed in the cucurbits 

 by Longo (2.7), and Kirkwood (13) has confirmed this point. 

 Longo found that the pollen tube expands into a large bulla at 



