FLORAL MODIFfCATlONS. 



1 



I 



of a different kind from the origiual, as iu 

 the case of the stamen of the Tilia, where 

 each of the 3 stamens left after suppres- 

 sion has divided into about 7, and has at 

 the same time yielded one or more little 

 petals fPig. 35 a) standing in front of the 

 group. Chorisis is thus seen to be Median 

 <in the case of the last mentioned petals) 

 or Lateral (in the case of the stamens), 

 accordiug to whether the line of separation 

 passes tan^entially or radially. Chorisis 

 may result in regular duplication (Stel- 

 laria) or irregular (Tilia). Regular dupli- 

 cation usually results from metamorpho- 

 sis, in ]ii* considered under law 5. 



When the number of organs of one kind, 

 as of petals, as in the rose (Fig. 47) or of 

 stamens (Fig. 46) exceeds twenty, it is 

 commonly spoken of as Indefinite, indi- 

 cated by the symbol. ^ although in most 

 cases it falls within certain definite upper 

 and lower limits which are of diagnostic 

 value- 



single part from which it was produced. 



The treatment of the subject of position 

 here presented is necessarily superficial 



and incomplete, owing to our failure to 

 have considered already the subject of 

 leaf arrangement. There is a direct co- 

 relation between the arrangement of foli- 

 age leaves and the parts of the flower. 

 As the arrangement of the former is some- 

 times by circles or whorls and souietimes 

 by spirals, it follows that some flowers 

 may be arranged on the former plan (Fig. 

 19), some (at least in part) upon the latter, 

 and such we actually find to be the case. 

 There is no one of the floral series but 

 what at times exhibits in its parts (in 

 most cases when they are numerous) a 

 well marked spiral arrangement. In spite 

 of these important facts the above pres- 

 entation has been made in view of its 

 great practical utility in pharmacognosti- 

 cal examinations. 

 The student should appreciate the neces- 



The numerical plan and deviations there- sity of examining the actual point of in- 



from are indicated pietorially by diagrams 

 like that shown in Fig. 27. and also by 

 formulae, for an explanation of which the 

 student should consult text-books. 



LA-W 2 — The parts of each circlealtcr- 

 nafe in position irith tliose of the circle 

 next ont^tde and of that ve,rt inside. In 

 other words, each part of the floorer 

 stands opposite a sinus of the adjacent 

 outer and inner circles. It is clear that 

 the parts of the two last mentioned cir- 

 cles must stand opposite each other or in 

 the same radial line (Fig. 28), and this 

 will be true of the parts of all alternating 

 circles. This law is also very prettily 

 illustrated by rhe two stamen-circles in 

 Fig. 28 a. It is also clear that if two 

 circles shall be brought into juxtaposition 

 by the supprt'sslon of an intervening circle, 

 their parts will naturally stand opposed 

 and thus appear to invalidate our sec- 

 ond 1m w. fis- in tlie cfjso of the stamens 

 and petals of Claytonia (Fig. 40). Cases 

 are even known in which such a condition 

 is supplemented by the addition of an 

 inner circle, whose stamens then stand 

 opposite the carpels. Note should also 

 be taken of the fact already pointed out, 

 that the cluster of organs produced by 

 chorisis corresponds in position with the 



sertion iu order to determine the position 

 of an organ, as the deviation in position 

 of its upper portion may easily lead to 



error, 

 LAW Z.— The part f^ comj)osh}g onccir- 



cle are all of the same form and equal 

 size A flower all of who?=e circles obey 

 this Ipw is Regular. An illustration is 

 found in the flower of Yeratrum (Fig. 25). 

 Irregularity may result from abortion 

 (Fig. 127), appendaging (Fig. 52), or mere 

 variation in form (Fig. 91), or size (Fig. 

 27 a). Sometimes, as in the last case, 

 the variation is so slight that the student 

 will be in doubt as to its existence, while 

 at other times an accidental variation in 

 an individual plant may suggest irregu- 

 larity where it is not a characteristic. 

 In cases of doubt the relationship of the 

 plant to others whose flowers are regular 

 or irregular may aid to a decision. 



LAW 4 ~ Each part of a circle drreJops 



separate and disconnected from allothers 



in that and in other circles 



As the mass oi tissue forming each of 

 the floral parts becondes isolated and 

 projected from the torus its margins and 

 faces are completely separate from those 

 of all adjacent parts. The law assumes 

 that growth shall continue in the iso- 



