318 OBSERVATIONS ON PROTANDRY AND PROTOGYNY. 



take place. Synacmy, or the contemporaneous maturing of tlie re- 

 productive organs, is nearly as frequent as protandry ; while protogyny 

 is a phenomenon of far less common occurrence. The two extremes 

 among the species observed may be stated to be Gmupanula rotundi- 

 folia and Scrophularia aquatica. In the Harebell, the pollen is dis- 

 charged long before the opening of the flower, so as to suggest the 

 idea of necessary self fertilization, were it not that the stigmas do not 

 open and become receptive until after the flower has been expanded 

 for some days, and is almost withering. Either, therefore, the pollen 

 must be retained in the flower by means of the hairs Avhich clothe the 

 style until the stigma is ready to receive it, or it must be carried by 

 insects to other flowers. In Scrophularia, on the other hand, the 

 stigma is itself mature in the bud, the stamens not discharging their 

 pollen until after the flower is open. It will be remarked that in some 

 Natural Orders, as LeguminoscB and Labiata, all the species examined, 

 with scarcely an exception, range themselves in one or other of the 

 three classes ; while in others, as Rosacefs, they are distributed over all 

 three, and in some instances, even closely allied species of the same 

 genus differ in this respect, as, for instance, Potentilla and Ranunculus. 

 Careful observation might even, in some cases, derive from this point 

 a useful diagnosis of difficult species. The following remarks may be 

 permitted on some species which afford points of special interest. 



In those Natural Orders in which the flowers are furnished with two 

 sets of stamens of different lengths, it is most usual for the longer ones 

 to discharge their pollen at an earlier period than the shorter ones, and 

 they probably have different functions to perform. This is commonly 

 the case with Cruciferce, Caryophyllece, Geraniacece, and Onagrariea, but 

 not, I believe, with Labiatoi ox Scrophularinece. The same phenomenon 

 is found in those Orders where the numerous stamens are arranged in 

 different whorls, as Ranunculacece and Rosacece. In the Strawberry 

 the mode in which different sets of stamens successively bend over 

 towards the pistil is very curious. In Ranunculus and Anemone the 

 outer rows of stamens first discharge their pollen extrorsely on to the 

 corolla or calyx, whence it is doubtless picked up by insects ; the 

 inner rows are discharged at a later period. 



In Ranunculus repens and Flammula the discharge of pollen com- 

 mences considerably before the stigma is ready ; in R. sceleratus the 

 reverse appears to be the case. Caryophylleous plants appear to have 



