1920] 



KA NDA — VERBENA 



65 



angustifolia comes ei 

 Le intermediate form 



same 



time. For this reason one 

 would expect that intermediate forms between V. angustifolia 

 and the other two species would be rather rare, while those between 

 V. stricta and V. hastata would be more common, if these inter- 

 mediate forms are really hybrids. As a matter of fact, the relative 

 abundance of the intermediates corresponded to the expectation. 

 The young ovule of V. hastata at the stage in which the mega- 

 spore mother cell first makes its appearance (fig. 15) is rounded 

 (fig. 58), while that of the other three forms is somewhat flattened, 

 as indicated in fig. 59. The young ovule of the intermediate form 

 is therefore similar to that of V. stricta. 



58 



Figs. 58, 59. — Diagrammatic outline of young ovule: fig. 58, V. hastata; fig. 59, 

 other 3 forms. 



The size of the mature embryo sac varies considerably within 

 each species owing to individual variations, but an approximate 

 comparison of its size at the same stage in the four forms can be 

 made without difficulty. The following table gives the average 

 length of 12 embryo sacs of the four forms at three different stages. 



TABLE II 



Name 



V. angustifolia 



Fig. 26 stage 

 Fig. 



Fig. 



V. stricta 



Intermediate form 



between V. stricta 



and V. hastata 



V. hastata 



51 stage 



^>i auige 



56 or 57 stage 



o . 260 mm 



0.500 



0.460 



0.225 mm 



0.460 



0.540 



0.185 mm. 



0.390 

 0.360 



0.185 mm 



0.310 

 0.340 



02-0. cu mm 



w The 



figures show that with regard to the length of the embryo sac the 

 intermediate form resembles V. hastata more than it does V. stricta. 



