I'litfcrs aiiif Roscii(hihl : f.ffrcts of frost. 159 



the Cottonwood trees had any fohage other than the few very large 

 leaves which had survived the frost. 



The various methods of recuperation can be readily seen in 

 the photographs of lilac (Fig. 2) and basswood (Fig. 3) branches 

 taken about a month after the frost. 



When the flowers or i^ower-buds were destroyed, the plant 

 usually produced no flowers during the season, but in some cases 

 (e. g. grape, both cultivated and native. Spiraea van Houttci) a 

 new crop of flower-buds appeared on the new growth produced 

 after the frost. In some cases the flowering habits of the plant 

 were completely disturbed. Thus Ribes aureum produced curious 

 abnormal inflorescences (long racemes with leafy bracts terminat- 

 ing the young twdgs) throughout the late summer and until hard 

 frost in late October. 



Sniniiiary. (1). Prolonged solid freezing will injure many 

 plants and parts of plants w^hich are not hurt by 2.5 degrees (C) 

 of frost. (2). Mechanical damage from loss of turgidity and 

 brittleness of frozen members is great. (3). Hard freezing is far 

 more destructive to our native woody plants than to our herba- 

 ceous vegetation. (4). Woody plants recover from hard freez- 

 ing very slowdy and produce very abnormal growth for the season 

 in which it occurs. 



EXPLANATION OF PLATE. 

 PLATE XXIII. 



Fig. 1. — A group of lilac bushes (Syriiiga znilgaris) on the L^niversity 

 Campus. The windward (northerly) side was fnlly exposed and the 

 leaves and twigs were killed. The leeward side was but slightly affected. 



Fig. 2. — ^Twig of lilac taken about a month after second frost, showing 

 method of recuperation. A number of injured leaves still remain attached. 



Fig. 3. — Twig of bassv/ood (Tilia auicricana) about a month after sec- 

 ond frost. A bud near the base of the current year's growth is unfolding; 

 the large leaf is one that survived the frost. 



