78 



MORPHOLOGY OF SPERMATOPHYTES 



ness with which these structures develop. We have obtained 

 exact information concerning this feature in Pinus Laricio. In 

 the spring, young ovules with distinct integument and niicellus 

 are found, but with no apparent differentiation of sporogenous 

 tissue. It should be remarked that at this season Strasburger ^* 

 found the mother cell differentiated in Larix, and suggested 

 that the ovule had passed the previous winter in this condi- 

 tion. In May the mother cell in Pinus becomes very apparent 

 through great increase in size. It is this stage which is to be 



Fio. 61.— Larix Europma : A, longitudinal section of a young ovule, showing the mega- 

 spore mother cell and tapetal cells, also at the left the beginning of the integument 

 (March 1st) ; B, first division of the mother cell ; C, the three cells derived from 

 the mother cell ; D, the beginning of the free nuclear division within the func- 

 tional megaspore ; x 150. — After Strasbuegeb. 



observed in the youngest evident cones, such as appear at the 

 very top of Fig. 53. In the following October the endosperm 

 has begun to develop, and is found as a parietal cytoplasmic 

 layer with few to numerous imbedded nuclei and a central 

 vacuole (Fig. 62), and in this condition the second winter 

 is passed. In the following spring the endosperm begins 

 to develop rapidly, and in June the archegonia are ready for 



