20 T. S. COBBOLI) ON THE EMBRYOLOGY OF ACHIMENES PICTA. 



larval nematoids in tlie leaves of these plants, and that the presence 

 of the worms is exceedingly injurious. 



As obtains in the majority of the gesnerworts, the species in 

 question is of a brilliant scarlet colour, and supplied with an 

 irregular five-lobed gamosepalous corolla ; the throat being 

 sufficiently capacious to admit the entrance of an ordinary bee. If 

 a flower be gathered a few days after the pollen grains have been 

 aj^plied to the capitate bilobed stigma, some of the tubular prolon- 

 gations of the intine will be found to have penetrated the loculus of 

 the capsule. How long the pollen tube takes to complete its so- 

 called germination I have not ascertained, but, judging from the 

 length of the stjde, it is probably not less than a week. Of course, 

 as Hofmeister has shown, the mere length of the style in any plant 

 is not by any means, of itself, a correct indication of the length of 

 time requisite for the completion of tubal growth. Thus, in Crocus 

 "we are told that the whole length of the style may, in extreme cases, 

 be traversed by the pollen tube in 24 hours, yet in the common 

 Ai'um maculatum, where the length of the style is less than the 

 eighth of an inch, Sachs says that the tube requires " at least five 

 days " to traverse the conducting tissue. In certain Orchids the 

 process takes ** several weeks or even months," in which cases 

 ovular development and pollen germination proceed simultaneously. 

 In Brugmansia and other long styled genera of the night shade 

 family, it seems to me that unless the process were comparatively 

 rapid, the flowering season itself would not be long enough to bring 

 about the essential phenomena of fertilisation. 



In Brugmansia sanguinea I have witnessed the early stage 

 of pollen germination, and the intine must extend itself 2,000 

 times the width of the grain in order to arrive at the micropyle of 

 the ovule. In Achimenes the pollen grains are very small, that is 

 about the y-oVTy" "^ diameter. In size and form they closely 

 correspond with a species of Gesneiia which I only examined last 

 week, and in which I found the grains to measure a trifle less than 

 ^-^" in diameter. Taking occasion to examine the pollen of 

 Eranthemum as belonging to a closely allied order {Acanthacece) I 

 found that the length of the grains extended up to the g^". 

 The ovules of the allied forms of Gesneria and Achimenes above 

 referred to, also closely corresponded in size, averaging about the 

 ■jjl-jj" from base to apex. Further, in connection with Brvgmansia, 

 I wish to say that I once noticed a pai^illary eminence projecting 



