THE ORIGIN OF " ZYGOMORPHISM." 



121 



plants, as Narcissus Corbularia. In Anagallis arvensis and 

 Lyclum harhariim tliez^e is nothing but an obliquity in the 

 style observable. 



In all the flowers which tend to show irregularities the 

 rule is that the corolla-limb stands in a vertical plane, so 

 that the flowers are visited from the front. This I take, as 

 mentioned above, to he generally a primary necessity for 

 bringing about irregularities of all kinds. There are some 

 campanulate and pendulous flowers where irregularity occurs 

 in the lengths of the filaments or the size of the anthers. 

 Thus, I have observed great fluctuations in the stamens of 

 Narcissus cermms : some of these I have illustrated in Fig. 37. 

 I noticed that a peduncle always 

 bore the same form in every 

 flower of its umbel. There 

 were mostly three flo"wers in 

 each, as of a, 6, and d; one 

 specimen of a and one of e had 

 only a single flower; and one 

 of c had two flowers. In a, b, 

 c, d, the three short stamens, 

 as well as the three long ones, 

 were all of the same height, respectively ; but in e one of the 

 shorter set was taller than the rest. 



Similar fluctuations are not at all uncommon in cultivated 

 heterostyled plants, as Primroses ; as will be alluded to again 

 in discussing the conditions of heterostylism. 



In Fritillaria Meleagris, though no irregularity occurs in 

 the perianth leaves, it often appears in the androecium, and 

 is more especially observable in the lengths of the anthers. 

 This would seem, therefore, to be another instance of 

 incipient change. 



Calluna vulgaris is likewise just commencing to be 

 13 



Fig. 37. — Xarcissus cernuus. 



