USE OF TRANSPARENT PARCHMENT PAPER BAGS. 267 
vulgaris, Lychnis vespertina and L. diurna, Papaver mudicaule and 
P. Rheas, Silene Armeria and S. noctiflora, and several other species and 
genera. 
In many cases it is certainly more convenient to carry out the fertilisa- 
tions in cages. Formerly I used small removable cages of wire gauze 
or tiffany, and now I have in my experimental garden a still larger 
cage made of fine wire gauze. But insects now and again can find their 
way in, either as eggs or larvee, existing on the trial plants or in the soil 
in the pots. I use, therefore, cages only in such cases when chance insect 
visits would not be detrimental to the results of the experiments. For 
fine work, however, I use exclusively these paper bags. 
In wet weather the parchment becomes damp and limp; it does not, 
however, tear. No water penetrates, and frequently after the rain it is 
found that considerable quantities of water have accumulated in the folds 
of the bags. Even in windy, stormy weather they are not torn unless 
sharp-pointed stakes are used with the plants, upon which the bags 
become impaled. Even in that case, however, the hole, which may 
result in weather at once windy and wet, and through which the stick 
protrudes, is practically stopped thereby, and hence even in this unfavour- 
able case no insect would, as a rule, find entry. 
The bags have furthermore the advantage that the particulars of the 
experiments concerned can be written upon them either with the so- 
called Indian nib or with pencil. 
Solitary flowers, which only need fertilising once, such as Poppies, 
form evidently the most convenient cases to handle. With Antirrhinwm 
and (Hnothera, I envelop the whole flowering stem in a bag and open 
this every two or three days in order to fertilise the fresh flowers or to 
castrate the new buds. Hach plant requires then usually two or three 
weeks before a sufficient quantity of seed is fertilised. But the frequent 
opening and closing of the bags does not damage them. 
To actual risks the flowers in these bags are only exceptionally 
exposed. For green leaves too little light penetrates, and thus they fade 
and become yellow; but only if the experiments be of long duration. 
Fraught with greater danger is the heat on hot August days. In the full 
blaze of the sun, the air in the bag can become so warm that the young 
half-grown flower buds drop off, and are thus lost for the continuance 
of the experiment. This often happens with Cnothera Lamarckiana. 
Or the flower buds concerned may die from drought, as occurs with 
Antirrhinum majus. Further, it appears that great heat is detri- 
mental to the formation of the pollen, as I found under such circum- 
stances that for several days in succession the young flowers of certain 
varieties of Gnothera Lamarckiana were without any pollen or had very 
little. 
It is possible that in such cases the perforated bags would suit better ; 
in rainy weather, however, they would plainly be less secure. 
I close my bags usually, not with metal clips, but with coarse string ; 
it is, however, not merely a question of excluding bees, humblebees, and 
flies, but also to guard against the entry of earwigs, which find shelter 
in their folds, and by devouring the pollen can often prove very detri- 
mental in cases of artificial self-pollination. 
