KikRKWooD: POLLEN-TUBE IN CUCURBITACEAE 329 
orchids, the difference in time being in no relation to the distance 
traversed. Among woody plants the time between pollination 
and fertilization has been observed to vary from one month 
(Betula*), to several months (Hamamelis)*, and Conrad’ has 
shown that it is over a year in Quercus. It has been shown that in 
those cases where a longer time is required the pollen-tube passes 
through a more or less protracted resting period; in these cases 
also the branching of tubes is more or less common, as appears in 
Pinus and the other cases above cited. 
Another phase of the development at this stage which has not 
received sufficient attention is the effect of the pollen-tube itself on 
the formation of the fruit, or the effect in some cases of a mere irri- 
tation of the stigma. Gaertner ™ reports that with certain plants he 
was able to obtain sterile fruits as large as normal ones by apply- 
ing to the stigmas the spores of Lycopodium, Tschermak™ reports 
various cases in the enlargement of the ovary by the use of pollen 
which did not fertilize the seed. Massart ® secured partial develop- 
ment of fruits in certain Cucurbitaceous forms by applying tritur- 
ated pollen to the stigmas. In these cases no seeds were fertilized 
and it appears that the pollen is the seat of an excitant which pene- 
trates the stigma and determines the survival of the ovary. Fur- 
thermore Leclerc du Sablon ® has found that the crossing of melons 
and cucumbers results in a considerable modification of the quan- 
tity and quality of the carbohydrates in the placenta and the 
pericarp, 
The Cucurbitaceae have long been under the observation of 
botanists, and certain features in the development of their fruit 
have frequently attracted attention. Soon after Amici’s discovery 
of the pollen-tube of Portulaca oleracea’ (1823), Brongniart® 
(1826) described a cellular conducting tissue in Cucurbita maxima 
Duch. and showed the pollen-tube traversing the beak of the nu- 
cellus. He observed that the “ spermatic granules”’ were trans- 
Ported by a canal formed of the intercellular spaces of the tissues 
of the pistil, 
Gaertner,’ in 1827, made observations on a number of plants 
and reported an acid secretion from the stigma in certain cases at 
the time of maturity, and also a correlation between the amount of 
Pollen on the stigma and the number of seeds produced, and that 
the number of seeds was increased by cross-fertilization. 
