PROTECTION OF SEEDS AGAINST WEATHER 447 



i^ easy to observe at Zermatt and A.rolla in the Pennine Alps, where this Pine 



grows, that the nut-crackers attack only the fully ripened siilc of even almost ripe 

 cones. As the cone ripens the seeds become easily accessible, but with their manner 

 of dispersal we shall deal in a later section of this work. Here we are concerned 

 only with the fact that many ovaries and fruit-envelopes render their contents 

 undesirable to animals by sticky secretions or disagreeable scents. The pods of 

 several Leguminosse, eg. species of Adenocarpus (A. decorticans, A. Hispanicus, 

 &c.), are invested both on their Hat sides and round the edge with short stalked, 

 sticky, brown glands, which are to be regarded as a protective arrangement for the 

 young pod. The same obtains in the Hemp {Cannabis sativa), though here it is 

 not the ovary but the scales immediately about it which are sticky and strongly 

 odorous. So also in the Hop (Humulus Xu^uJws), the fruits are invested in scales 

 hearing glands which play a like part. Even the ubiquitous sparrow leaves the 

 fruits of these two plants alone during the period of ripening. 



Of not less importance to the young embryo is protection against injurious 

 climatic influences. Among these, undue moisture and dryness are the chief; and 

 it is to be expected that due provision against them should be made on behalf of the 

 young plant whilst it remains on the parent. Seeds contained in berries, drupes, 

 and indehiscent fruits, as well as those which, produced in capsules, are dispersed 

 at the moment of fruit- dehiscence, hardly come under consideration here, as the 

 opportunities for hurt by weather are relatively small. But in the case of dehiscent 

 fruits which open by means of valves, teeth, or pores, and in which the seeds are 

 retained for some time after the opening of the fruit before they are scattered, 

 provision must be made against the entrance of rain into the cavity of the fruit, 

 which might injure the seeds. This class of danger is averted by the fact that the 

 various valves, teeth, &c, which guard the apertures of the fruits, are very hygro- 

 scopic and close in humid weather; or, what is equivalent to this, they only open in 

 dry weather, especially under the influence of drying winds. To make this remark- 

 able contrivance intelligible we must briefly describe the arrangements for seed- 

 dispersal obtaining in capsules of the kind. Capsules opening by valves, teeth, &c, 

 are usually inserted on long stalks, or, if sessile, the axis from which they arise 

 possesses considerable length. These stalks are fairly stiff", and oscillating to and 

 fro in gusts of wind the contained seeds are shaken out, usually as the capsule 

 springs back after the blast. In the case, for instance, of the beaker-like capsules 

 of the Nottingham Catchfly (Silene nutans, fig. 340 5 ) the seeds cannot fall out 

 of their own accord, the opening being directed upwards; but as soon as the wind 

 ' the long stalk in vibration they are jerked out. For this mode of scattering 

 of the seeds it is essential that the apertures of the fruit should be directed 

 upwards. Indeed, in the great majority of cases of this class, this is their position. 

 In this Catchfly at the time of flowering the flower-stalks are pendent (see figs. 

 •J:i^ and 239, pp. 154 and 155), but, as the fruit ripens, the fruit-stalk becomes 

 erect: the same thing is well shown in the .Martagon lily. On the other hand, 

 when the fruit-stalk bends down after (lowering, as in the liellllower (Ciunjinuiiln, 



