EXOGENS. 325 



Sub-Class II. HYPOGYNOUS EXOGENS. 



The hypogpious insertion of the stamens has been regarded by the French school of 

 Botanists as one of very great systematical importance ; and it does seem to collect 

 together a large mass of plants the genera of which have a great resemblance to each 

 other. If we assume that the entire separation of the calyx and corolla from the sta- 

 mens is an indication of those organs being in hypogynous plants of less importance 

 than usual, then the character acquires a pliysiological value not previously assigned to 

 it. And such appears to be the case ; for it is only among hypogynous Exogens that 

 we find a total absence of floral envelopes, as in the Piperal and Chenopodal AUiances; 

 it is among them that the presence of petals seems to be of least moment, as the cha- 

 racter of a Natural Order ; for in 12 AUiances out of 14, petals are either constantly or 

 frequently absent, and in one only are they often combined into a tube ; in all other 

 cases such a circumstance is exceptional. 



It is, however, found that in some cases plants with a perigjTious insertion of the 

 stamens will nevertheless combine with hypogjTious AlUances ; as happens in the case 

 of Samyds among Violals, and here and there in the Erical, Silenal, and Chenopodal 

 Alliances ; but these again seem to be mere exceptional instances not affecting the 

 general value of the hypog;yTious character, even where it is certain that the Orders in 

 wlaich such exceptions occiu- are rightly placed. Experience shows too that all uatm'al 

 groups of plants come in contact here and there ; and hi such instances exceptions to 

 habitual structiu-e make theu* appearance. It will be found, moreover, that the perigy- 

 nous Orders or genera here and there introduced among the hypogjTious series refuse 

 to associate with any part of the perigynous Sub-class. Thus Samyds, a perigynous 

 fonn of Violals, have no locus standi in any perigynous Alliance, while then- affinity to 

 the hypogynous Violals is of an obvious natm'e. 



The sequence observed in the arrangement of the Alliances iscliiefly objectionable on 

 account of the'presence of Berberals in contact with Ericals ; but if we regard Cyrillads 

 and Pittosporads as Berberals, then the Erical Humiriads join them perfectly ; but these 

 approximations have not yet received the sanction of Botanists,and depend for theii* justi- 

 fication upon giving a higher value than customary to the presence of a small embryo 

 in copious albumen. 



There can be no doubt about the closeness of the relationship borne by the diclinous 

 Papayals to the hypogynous Violals, and therefore it is mth the latter that the hypo- 

 g}Tious series is made to begin. The transition from Violals to Cistals, thence to Mal- 

 vals, to Sapindals, and to Guttiferals is so much in confonnity to the ^'iews generally 

 entertained by Botanists, that no objection to it is anticipated. The next step to N}Tn- 

 phals is more open to criticism ; but if Tutsans are taken as an extreme form of Gutti- 

 ferals, there is no difficulty in admitting the justice of bringing NjTiiphals into contact 

 with them. The next relationship, that of Raiials, is obvious ; their Poppyworts possess a 

 genus, Hypecoum, which stands on the limits of Fumeworts among Berberals ; thence 

 either C}Tillads or Olacads will join the chain to Humiriads among Ericals. In the 

 latter Alliance Heathworts themselves come distinctly in contact with such monopetal- 

 ous Rueworts as Correa. Geranials join Rutals by means of Oxahds, and Silenals 

 through Flaxworts ; and, finally, the Chenopodal and Piperal Alliances are apparently 

 degraded forms of the Silenal Alhance. Piperals ought, however, to be regarded as a 

 lateral offset from Chenopodals rather than as an Order in the dii-ect luie of succession 

 to the perigynous Sub-class. 



