Botanical Garden of University op Amsterdam. 55 



roof, quite as in an ordinary greenhouse. This garden house, 

 which is about fifteen meters wide and thirty meters long, has 

 board walls that are about three meters high. The gently slop- 

 ing roof is supported by iron beams, and the whole building is 

 strengthened by transverse iron rods at the top of the walls. 

 Three sides of this house are closed continually, but one side may 

 be opened or closed as desired. It is thus possible to grow plants 

 in this part of the experimental garden under conditions, and at 

 times, that would not be possible out of doors. By noticing the 

 photograph it will be seen that the primroses are arranged in 



rectangular beds in which, 

 when the young plants were 

 first set out, they were ar- 

 ranged in absolute order. 



The entire roof and sides 

 of the part of the garden, 

 shown in Figure 1, is cov- 

 ered by a rather coarse-mesh- 

 ed wire net, supported, as 

 shown in the photograph, by 

 vertical iron posts about three 

 meters in height. By no- 

 ticing this photograph care- 

 fully the meshes of the net 

 can easily be seen. The pur- 

 pose of this sort of a net-like 

 protection over the plants, 

 is to keep out birds and other 

 creatures that would inter- 

 fere with the plants under ex- 

 perimentation. At the same 

 time light and air are freely 

 admitted. The part of the garden thus covered bv wire netting 

 is considerably larger than the part covered by glass, being about 

 sixty by sixty meters. As already indicated the arrangement of 

 the plants in beds is well shown in Figure 1. These beds are 



about two meters wide and four meters long. Great care is 

 taken in the sterilization of the soil for these beds, and the plant- 

 ing of the young plants. The beds in the foreground show with 



2 Professor de Vries in the garden. 



